Absolute Value
 Inequalities
What is Absolute Value?
What is Absolute Value?
• Absolute Value is the distance from zero on a
 number line.
What is Absolute Value?
• Absolute Value is the distance from zero on a
 number line.
• Distance is always positive.
What is Absolute Value?
• Absolute Value is the distance from zero on a
 number line.
• Distance is always positive.
• Symbol is | |.
What is Absolute Value?
• Absolute Value is the distance from zero on a
 number line.
• Distance is always positive.
• Symbol is | |.                       • Example 1: |3| = 3


                   -5   -4   -3   -2   -1   0   1   2   3   4   5
What is Absolute Value?
• Absolute Value is the distance from zero on a
 number line.
• Distance is always positive.
• Symbol is | |.                       • Example 1: |3| = 3


                   -5   -4   -3   -2   -1   0   1   2   3   4   5
What is Absolute Value?
• Absolute Value is the distance from zero on a
 number line.
• Distance is always positive.
• Symbol is | |.                       • Example 1: |3| = 3


                   -5   -4   -3   -2   -1   0    1    2    3   4   5



• Example 2: |-3| = 3
                                  -5   -4   -3   -2   -1   0   1   2   3   4   5
What is Absolute Value?
• Absolute Value is the distance from zero on a
 number line.
• Distance is always positive.
• Symbol is | |.                       • Example 1: |3| = 3


                   -5   -4   -3   -2   -1   0    1    2    3   4   5



• Example 2: |-3| = 3
                                  -5   -4   -3   -2   -1   0   1   2   3   4   5
Absolute Value Equation
Absolute Value Equation
• Because the distance can be towards the
 positive or negative direction, Absolute Value
 Equations must account for both cases.
Absolute Value Equation
• Because the distance can be towards the
 positive or negative direction, Absolute Value
 Equations must account for both cases.
• Example 3: |x| = 4
Absolute Value Equation
• Because the distance can be towards the
 positive or negative direction, Absolute Value
 Equations must account for both cases.
• Example 3: |x| = 4

 x = 4 or        -5   -4   -3   -2   -1   0   1   2   3   4   5
Absolute Value Equation
• Because the distance can be towards the
 positive or negative direction, Absolute Value
 Equations must account for both cases.
• Example 3: |x| = 4

 x = 4 or        -5   -4   -3   -2   -1   0   1   2   3   4   5


  -(x) = 4
Absolute Value Equation
• Because the distance can be towards the
 positive or negative direction, Absolute Value
 Equations must account for both cases.
• Example 3: |x| = 4

 x = 4 or        -5   -4        -3        -2        -1        0        1       2       3       4       5


  -(x) = 4
    x = -4
                           -5        -4        -3        -2       -1       0       1       2       3       4   5
Absolute Value Inequality
Absolute Value Inequality
• How does Absolute Value work for Inequalities?
Absolute Value Inequality
• How does Absolute Value work for Inequalities?
• Example 4: |x| < 4
Absolute Value Inequality
• How does Absolute Value work for Inequalities?
• Example 4: |x| < 4

Write the inequalities for the 2 cases and solve.
Absolute Value Inequality
• How does Absolute Value work for Inequalities?
• Example 4: |x| < 4

Write the inequalities for the 2 cases and solve.
 Positive Case
Absolute Value Inequality
• How does Absolute Value work for Inequalities?
• Example 4: |x| < 4

Write the inequalities for the 2 cases and solve.
 Positive Case            Negative Case
Absolute Value Inequality
• How does Absolute Value work for Inequalities?
• Example 4: |x| < 4

Write the inequalities for the 2 cases and solve.
 Positive Case            Negative Case
    x<4                      -(x) < 4
Absolute Value Inequality
• How does Absolute Value work for Inequalities?
• Example 4: |x| < 4

Write the inequalities for the 2 cases and solve.
 Positive Case            Negative Case
    x<4                      -(x) < 4
                               x > -4
Absolute Value Inequality
• How does Absolute Value work for Inequalities?
• Example 4: |x| < 4

Write the inequalities for the 2 cases and solve.
 Positive Case             Negative Case
    x<4                       -(x) < 4
                                x > -4

 Remember to reverse the inequality when
 dividing by a negative.
Example 4 (con’t)
         |x| < 4




-5   -4   -3   -2   -1   0   1   2   3   4   5
Example 4 (con’t)
                     |x| < 4
• Graph the solutions.




            -5   -4   -3   -2   -1   0   1   2   3   4   5
Example 4 (con’t)
                     |x| < 4
• Graph the solutions.

      x<4


            -5   -4   -3   -2   -1   0   1   2   3   4   5
Example 4 (con’t)
                     |x| < 4
• Graph the solutions.

      x<4                  x > -4


            -5   -4   -3   -2   -1   0   1   2   3   4   5
Example 4 (con’t)
                      |x| < 4
• Graph the solutions.

       x<4                  x > -4


             -5   -4   -3   -2   -1   0   1   2   3   4   5



• Is the solution is an intersection (∩) or a union (∪)?
Example 4 (con’t)
                      |x| < 4
• Graph the solutions.

       x<4                  x > -4


             -5   -4   -3   -2   -1   0   1   2   3   4   5



• Is the solution is an intersection (∩) or a union (∪)?
• Check numbers in the original inequality to help
 you decide.
Example 4 (con’t)
     |x| < 4

-5   -4   -3   -2   -1   0   1   2   3   4   5
Example 4 (con’t)
                      |x| < 4

                 -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x < 4, one that solves x
  > -4, and one that solves both inequalities.
Example 4 (con’t)
                      |x| < 4

                 -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x < 4, one that solves x
  > -4, and one that solves both inequalities.

• Check 0 first. Why zero? Because it’s easy. ☺
Example 4 (con’t)
                      |x| < 4

                 -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x < 4, one that solves x
  > -4, and one that solves both inequalities.

• Check 0 first. Why zero? Because it’s easy. ☺
    |0| < 4 True, so the area between -4 and 4 is a solution.
Example 4 (con’t)
                      |x| < 4

                 -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x < 4, one that solves x
  > -4, and one that solves both inequalities.

• Check 0 first. Why zero? Because it’s easy. ☺
    |0| < 4 True, so the area between -4 and 4 is a solution.
• Check -5.
Example 4 (con’t)
                      |x| < 4

                 -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x < 4, one that solves x
  > -4, and one that solves both inequalities.

• Check 0 first. Why zero? Because it’s easy. ☺
    |0| < 4 True, so the area between -4 and 4 is a solution.
• Check -5.
    |-5| < 4 False, so the area less than -4 is not a solution.
Example 4 (con’t)
                      |x| < 4

                 -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x < 4, one that solves x
  > -4, and one that solves both inequalities.

• Check 0 first. Why zero? Because it’s easy. ☺
    |0| < 4 True, so the area between -4 and 4 is a solution.
• Check -5.
    |-5| < 4 False, so the area less than -4 is not a solution.
• Check 5.
Example 4 (con’t)
                      |x| < 4

                 -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x < 4, one that solves x
  > -4, and one that solves both inequalities.

• Check 0 first. Why zero? Because it’s easy. ☺
    |0| < 4 True, so the area between -4 and 4 is a solution.
• Check -5.
    |-5| < 4 False, so the area less than -4 is not a solution.
• Check 5.
    |5| < 4 False, so the area greater than 4 is not a solution.
Example 4 (con’t)
                    |x| < 4

               -5   -4   -3   -2   -1   0   1   2   3   4   5

• Because the only number that worked was between
 -4 and 4, the solution is an intersection.
Example 4 (con’t)
                    |x| < 4

               -5   -4   -3   -2   -1   0   1   2   3   4   5

• Because the only number that worked was between
 -4 and 4, the solution is an intersection.

• The solution can be written as
Example 4 (con’t)
                    |x| < 4

               -5   -4   -3    -2   -1   0   1   2   3   4   5

• Because the only number that worked was between
 -4 and 4, the solution is an intersection.

• The solution can be written as

                              {x | -4 < x < 4}
Example 4 (con’t)
                    |x| < 4

               -5   -4   -3    -2   -1   0   1   2   3   4   5

• Because the only number that worked was between
 -4 and 4, the solution is an intersection.

• The solution can be written as

                              {x | -4 < x < 4}

   or as
Example 4 (con’t)
                    |x| < 4

               -5   -4   -3    -2   -1   0   1   2   3   4   5

• Because the only number that worked was between
 -4 and 4, the solution is an intersection.

• The solution can be written as

                              {x | -4 < x < 4}

   or as

                         {x | x > -4 ∩ x < 4}
Example 5: What about |x| > 3?
Example 5: What about |x| > 3?
Write the inequalities for the 2 cases and solve.
Example 5: What about |x| > 3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
Example 5: What about |x| > 3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
    x>3                      -(x) > 3
Example 5: What about |x| > 3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
    x>3                      -(x) > 3
                               x < -3
Example 5: What about |x| > 3?
Write the inequalities for the 2 cases and solve.

 Positive Case             Negative Case
    x>3                       -(x) > 3
                                x < -3

 Remember to reverse the inequality when
 dividing by a negative.
Example 5: What about |x| > 3?
Write the inequalities for the 2 cases and solve.

 Positive Case                       Negative Case
    x>3                                 -(x) > 3
                                          x < -3

 Remember to reverse the inequality when
 dividing by a negative.

• Graph.
                 -5   -4   -3   -2    -1   0   1   2   3   4   5
Example 5: What about |x| > 3?
Write the inequalities for the 2 cases and solve.

 Positive Case                       Negative Case
    x>3                                 -(x) > 3
                                          x < -3

 Remember to reverse the inequality when
 dividing by a negative.

• Graph.
                 -5   -4   -3   -2    -1   0   1   2   3   4   5
Example 5: What about |x| > 3?
Write the inequalities for the 2 cases and solve.

 Positive Case                       Negative Case
    x>3                                 -(x) > 3
                                          x < -3

 Remember to reverse the inequality when
 dividing by a negative.

• Graph.
                 -5   -4   -3   -2    -1   0   1   2   3   4   5
Example 5 (con’t): |x| > 3
     -5   -4   -3   -2   -1   0   1   2   3   4   5
Example 5 (con’t): |x| > 3
              -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x > 3, one that solves x < 3,
  and one that neither inequality.
Example 5 (con’t): |x| > 3
              -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x > 3, one that solves x < 3,
  and one that neither inequality.

• Check 0 first. Why zero? Because it’s easy. ☺
Example 5 (con’t): |x| > 3
              -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x > 3, one that solves x < 3,
  and one that neither inequality.

• Check 0 first. Why zero? Because it’s easy. ☺
     |0| > 3 False, so the area between -4 and 4 is not a solution.
Example 5 (con’t): |x| > 3
              -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x > 3, one that solves x < 3,
  and one that neither inequality.

• Check 0 first. Why zero? Because it’s easy. ☺
     |0| > 3 False, so the area between -4 and 4 is not a solution.
• Check -5.
Example 5 (con’t): |x| > 3
              -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x > 3, one that solves x < 3,
  and one that neither inequality.

• Check 0 first. Why zero? Because it’s easy. ☺
     |0| > 3 False, so the area between -4 and 4 is not a solution.
• Check -5.
     |-5| > 3 True, so the area less than -4 is a solution.
Example 5 (con’t): |x| > 3
              -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x > 3, one that solves x < 3,
  and one that neither inequality.

• Check 0 first. Why zero? Because it’s easy. ☺
     |0| > 3 False, so the area between -4 and 4 is not a solution.
• Check -5.
     |-5| > 3 True, so the area less than -4 is a solution.
• Check 5.
Example 5 (con’t): |x| > 3
              -5   -4   -3   -2   -1   0   1   2   3   4   5

• Check 3 numbers. One that solves x > 3, one that solves x < 3,
  and one that neither inequality.

• Check 0 first. Why zero? Because it’s easy. ☺
     |0| > 3 False, so the area between -4 and 4 is not a solution.
• Check -5.
     |-5| > 3 True, so the area less than -4 is a solution.
• Check 5.
     |5| > 3 True, so the area greater than 4 is a solution.
Example 5 (con’t): |x| > 3
     -5   -4   -3   -2   -1   0   1   2   3   4   5
Example 5 (con’t): |x| > 3
           -5   -4   -3   -2   -1   0   1   2   3   4   5


• Because a number worked from both
 inequalities, the solution is an union.
Example 5 (con’t): |x| > 3
           -5   -4   -3   -2   -1   0   1   2   3   4   5


• Because a number worked from both
 inequalities, the solution is an union.

• The solution can be written as
Example 5 (con’t): |x| > 3
           -5   -4   -3    -2   -1   0   1   2   3   4   5


• Because a number worked from both
 inequalities, the solution is an union.

• The solution can be written as

                          {x | x < -3 ∪ x > 3}
Example 6: What about |x| < -3?
Example 6: What about |x| < -3?
Write the inequalities for the 2 cases and solve.
Example 6: What about |x| < -3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
Example 6: What about |x| < -3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
   x < -3                   -(x) < -3
Example 6: What about |x| < -3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
   x < -3                   -(x) < -3
                               x>3
Example 6: What about |x| < -3?
Write the inequalities for the 2 cases and solve.

 Positive Case                           Negative Case
   x < -3                                  -(x) < -3
                                              x>3

• Graph.

            -5   -4   -3   -2   -1   0    1   2   3   4   5
Example 6: What about |x| < -3?
Write the inequalities for the 2 cases and solve.

 Positive Case                           Negative Case
   x < -3                                  -(x) < -3
                                              x>3

• Graph.

            -5   -4   -3   -2   -1   0    1   2   3   4   5
Example 6: What about |x| < -3?
Write the inequalities for the 2 cases and solve.

 Positive Case                           Negative Case
   x < -3                                  -(x) < -3
                                              x>3

• Graph.

            -5   -4   -3   -2   -1   0    1   2   3   4   5
Example 6 (con’t): |x| < -3
     -5   -4   -3   -2   -1   0   1   2   3   4   5
Example 6 (con’t): |x| < -3
             -5   -4   -3   -2   -1   0   1   2   3   4   5


• It looks a lot like Example 5 so far.
  Time for our check. Let’s check -4 first.
Example 6 (con’t): |x| < -3
             -5   -4   -3   -2   -1   0   1   2   3   4   5


• It looks a lot like Example 5 so far.
  Time for our check. Let’s check -4 first.                           ?
                                                              − ( −4 ) <− 3
                                                                4 < −3
                                                                4 < −3
Example 6 (con’t): |x| < -3
             -5   -4   -3   -2   -1   0   1   2   3   4   5


• It looks a lot like Example 5 so far.
  Time for our check. Let’s check -4 first.                           ?
                                                              − ( −4 ) <− 3
• What?! This isn’t true!                                       4 < −3
                                                                4 < −3
Example 6 (con’t): |x| < -3
             -5   -4   -3   -2   -1   0   1   2   3   4   5


• It looks a lot like Example 5 so far.
  Time for our check. Let’s check -4 first.                           ?
                                                              − ( −4 ) <− 3
• What?! This isn’t true!                                       4 < −3
• Absolute Value is distance. Distance is                       4 < −3
  never negative. The Absolute Value
  can never result in a negative number.
Example 6 (con’t): |x| < -3
             -5   -4   -3   -2   -1   0   1   2   3   4   5


• It looks a lot like Example 5 so far.
  Time for our check. Let’s check -4 first.                           ?
                                                              − ( −4 ) <− 3
• What?! This isn’t true!                                       4 < −3
• Absolute Value is distance. Distance is                       4 < −3
  never negative. The Absolute Value
  can never result in a negative number. No Solution
Example 7: What about |x| > -3?
Example 7: What about |x| > -3?
Write the inequalities for the 2 cases and solve.
Example 7: What about |x| > -3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
Example 7: What about |x| > -3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
   x > -3                   -(x) > -3
Example 7: What about |x| > -3?
Write the inequalities for the 2 cases and solve.

 Positive Case            Negative Case
   x > -3                   -(x) > -3
                               x<3
Example 7: What about |x| > -3?
Write the inequalities for the 2 cases and solve.

 Positive Case                           Negative Case
   x > -3                                  -(x) > -3
                                              x<3

• Graph.

            -5   -4   -3   -2   -1   0    1   2   3   4   5
Example 7: What about |x| > -3?
Write the inequalities for the 2 cases and solve.

 Positive Case                           Negative Case
   x > -3                                  -(x) > -3
                                              x<3

• Graph.

            -5   -4   -3   -2   -1   0    1   2   3   4   5
Example 7: What about |x| > -3?
Write the inequalities for the 2 cases and solve.

 Positive Case                           Negative Case
   x > -3                                  -(x) > -3
                                              x<3

• Graph.

            -5   -4   -3   -2   -1   0    1   2   3   4   5
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3   4   5

• What is different about the graph?
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3   4   5

• What is different about the graph?

• Check 0.
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3   4       5

• What is different about the graph?                         ?
                                                         0 >− 3
• Check 0.
                                                         0 > −3
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3   4       5

• What is different about the graph?                         ?
                                                         0 >− 3
• Check 0.
                                                         0 > −3
• Looks good. Try -5.
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3   4       5

• What is different about the graph?                         ?
                                                         0 >− 3
• Check 0.
                                                         0 > −3         ?
                                                                     −5 >− 3
• Looks good. Try -5.
                                                                     5 > −3
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3   4       5

• What is different about the graph?                         ?
                                                         0 >− 3
• Check 0.
                                                         0 > −3         ?
                                                                     −5 >− 3
• Looks good. Try -5.
                                                                     5 > −3
• Also looks good.
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3   4       5

• What is different about the graph?                         ?
                                                         0 >− 3
• Check 0.
                                                         0 > −3         ?
                                                                     −5 >− 3
• Looks good. Try -5.
                                                                     5 > −3
• Also looks good.

• Is there a number that will not work in the original problem?
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3   4       5

• What is different about the graph?                         ?
                                                         0 >− 3
• Check 0.
                                                         0 > −3         ?
                                                                     −5 >− 3
• Looks good. Try -5.
                                                                     5 > −3
• Also looks good.

• Is there a number that will not work in the original problem?

• No, which means the solution can be any real number.
Example 7 (con’t): |x| > -3
                -5   -4   -3   -2   -1   0   1   2   3    4       5

• What is different about the graph?                          ?
                                                          0 >− 3
• Check 0.
                                                          0 > −3         ?
                                                                      −5 >− 3
• Looks good. Try -5.
                                                                      5 > −3
• Also looks good.

• Is there a number that will not work in the original problem?

• No, which means the solution can be any real number.

                                                         All Real Numbers

Absolute Value Inequalities Notes

  • 1.
  • 2.
  • 3.
    What is AbsoluteValue? • Absolute Value is the distance from zero on a number line.
  • 4.
    What is AbsoluteValue? • Absolute Value is the distance from zero on a number line. • Distance is always positive.
  • 5.
    What is AbsoluteValue? • Absolute Value is the distance from zero on a number line. • Distance is always positive. • Symbol is | |.
  • 6.
    What is AbsoluteValue? • Absolute Value is the distance from zero on a number line. • Distance is always positive. • Symbol is | |. • Example 1: |3| = 3 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 7.
    What is AbsoluteValue? • Absolute Value is the distance from zero on a number line. • Distance is always positive. • Symbol is | |. • Example 1: |3| = 3 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 8.
    What is AbsoluteValue? • Absolute Value is the distance from zero on a number line. • Distance is always positive. • Symbol is | |. • Example 1: |3| = 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Example 2: |-3| = 3 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 9.
    What is AbsoluteValue? • Absolute Value is the distance from zero on a number line. • Distance is always positive. • Symbol is | |. • Example 1: |3| = 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Example 2: |-3| = 3 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 10.
  • 11.
    Absolute Value Equation •Because the distance can be towards the positive or negative direction, Absolute Value Equations must account for both cases.
  • 12.
    Absolute Value Equation •Because the distance can be towards the positive or negative direction, Absolute Value Equations must account for both cases. • Example 3: |x| = 4
  • 13.
    Absolute Value Equation •Because the distance can be towards the positive or negative direction, Absolute Value Equations must account for both cases. • Example 3: |x| = 4 x = 4 or -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 14.
    Absolute Value Equation •Because the distance can be towards the positive or negative direction, Absolute Value Equations must account for both cases. • Example 3: |x| = 4 x = 4 or -5 -4 -3 -2 -1 0 1 2 3 4 5 -(x) = 4
  • 15.
    Absolute Value Equation •Because the distance can be towards the positive or negative direction, Absolute Value Equations must account for both cases. • Example 3: |x| = 4 x = 4 or -5 -4 -3 -2 -1 0 1 2 3 4 5 -(x) = 4 x = -4 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 16.
  • 17.
    Absolute Value Inequality •How does Absolute Value work for Inequalities?
  • 18.
    Absolute Value Inequality •How does Absolute Value work for Inequalities? • Example 4: |x| < 4
  • 19.
    Absolute Value Inequality •How does Absolute Value work for Inequalities? • Example 4: |x| < 4 Write the inequalities for the 2 cases and solve.
  • 20.
    Absolute Value Inequality •How does Absolute Value work for Inequalities? • Example 4: |x| < 4 Write the inequalities for the 2 cases and solve. Positive Case
  • 21.
    Absolute Value Inequality •How does Absolute Value work for Inequalities? • Example 4: |x| < 4 Write the inequalities for the 2 cases and solve. Positive Case Negative Case
  • 22.
    Absolute Value Inequality •How does Absolute Value work for Inequalities? • Example 4: |x| < 4 Write the inequalities for the 2 cases and solve. Positive Case Negative Case x<4 -(x) < 4
  • 23.
    Absolute Value Inequality •How does Absolute Value work for Inequalities? • Example 4: |x| < 4 Write the inequalities for the 2 cases and solve. Positive Case Negative Case x<4 -(x) < 4 x > -4
  • 24.
    Absolute Value Inequality •How does Absolute Value work for Inequalities? • Example 4: |x| < 4 Write the inequalities for the 2 cases and solve. Positive Case Negative Case x<4 -(x) < 4 x > -4 Remember to reverse the inequality when dividing by a negative.
  • 25.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 26.
    Example 4 (con’t) |x| < 4 • Graph the solutions. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 27.
    Example 4 (con’t) |x| < 4 • Graph the solutions. x<4 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 28.
    Example 4 (con’t) |x| < 4 • Graph the solutions. x<4 x > -4 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 29.
    Example 4 (con’t) |x| < 4 • Graph the solutions. x<4 x > -4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Is the solution is an intersection (∩) or a union (∪)?
  • 30.
    Example 4 (con’t) |x| < 4 • Graph the solutions. x<4 x > -4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Is the solution is an intersection (∩) or a union (∪)? • Check numbers in the original inequality to help you decide.
  • 31.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 32.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x < 4, one that solves x > -4, and one that solves both inequalities.
  • 33.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x < 4, one that solves x > -4, and one that solves both inequalities. • Check 0 first. Why zero? Because it’s easy. ☺
  • 34.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x < 4, one that solves x > -4, and one that solves both inequalities. • Check 0 first. Why zero? Because it’s easy. ☺ |0| < 4 True, so the area between -4 and 4 is a solution.
  • 35.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x < 4, one that solves x > -4, and one that solves both inequalities. • Check 0 first. Why zero? Because it’s easy. ☺ |0| < 4 True, so the area between -4 and 4 is a solution. • Check -5.
  • 36.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x < 4, one that solves x > -4, and one that solves both inequalities. • Check 0 first. Why zero? Because it’s easy. ☺ |0| < 4 True, so the area between -4 and 4 is a solution. • Check -5. |-5| < 4 False, so the area less than -4 is not a solution.
  • 37.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x < 4, one that solves x > -4, and one that solves both inequalities. • Check 0 first. Why zero? Because it’s easy. ☺ |0| < 4 True, so the area between -4 and 4 is a solution. • Check -5. |-5| < 4 False, so the area less than -4 is not a solution. • Check 5.
  • 38.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x < 4, one that solves x > -4, and one that solves both inequalities. • Check 0 first. Why zero? Because it’s easy. ☺ |0| < 4 True, so the area between -4 and 4 is a solution. • Check -5. |-5| < 4 False, so the area less than -4 is not a solution. • Check 5. |5| < 4 False, so the area greater than 4 is not a solution.
  • 39.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Because the only number that worked was between -4 and 4, the solution is an intersection.
  • 40.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Because the only number that worked was between -4 and 4, the solution is an intersection. • The solution can be written as
  • 41.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Because the only number that worked was between -4 and 4, the solution is an intersection. • The solution can be written as {x | -4 < x < 4}
  • 42.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Because the only number that worked was between -4 and 4, the solution is an intersection. • The solution can be written as {x | -4 < x < 4} or as
  • 43.
    Example 4 (con’t) |x| < 4 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Because the only number that worked was between -4 and 4, the solution is an intersection. • The solution can be written as {x | -4 < x < 4} or as {x | x > -4 ∩ x < 4}
  • 44.
    Example 5: Whatabout |x| > 3?
  • 45.
    Example 5: Whatabout |x| > 3? Write the inequalities for the 2 cases and solve.
  • 46.
    Example 5: Whatabout |x| > 3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case
  • 47.
    Example 5: Whatabout |x| > 3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x>3 -(x) > 3
  • 48.
    Example 5: Whatabout |x| > 3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x>3 -(x) > 3 x < -3
  • 49.
    Example 5: Whatabout |x| > 3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x>3 -(x) > 3 x < -3 Remember to reverse the inequality when dividing by a negative.
  • 50.
    Example 5: Whatabout |x| > 3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x>3 -(x) > 3 x < -3 Remember to reverse the inequality when dividing by a negative. • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 51.
    Example 5: Whatabout |x| > 3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x>3 -(x) > 3 x < -3 Remember to reverse the inequality when dividing by a negative. • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 52.
    Example 5: Whatabout |x| > 3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x>3 -(x) > 3 x < -3 Remember to reverse the inequality when dividing by a negative. • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 53.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 54.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x > 3, one that solves x < 3, and one that neither inequality.
  • 55.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x > 3, one that solves x < 3, and one that neither inequality. • Check 0 first. Why zero? Because it’s easy. ☺
  • 56.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x > 3, one that solves x < 3, and one that neither inequality. • Check 0 first. Why zero? Because it’s easy. ☺ |0| > 3 False, so the area between -4 and 4 is not a solution.
  • 57.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x > 3, one that solves x < 3, and one that neither inequality. • Check 0 first. Why zero? Because it’s easy. ☺ |0| > 3 False, so the area between -4 and 4 is not a solution. • Check -5.
  • 58.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x > 3, one that solves x < 3, and one that neither inequality. • Check 0 first. Why zero? Because it’s easy. ☺ |0| > 3 False, so the area between -4 and 4 is not a solution. • Check -5. |-5| > 3 True, so the area less than -4 is a solution.
  • 59.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x > 3, one that solves x < 3, and one that neither inequality. • Check 0 first. Why zero? Because it’s easy. ☺ |0| > 3 False, so the area between -4 and 4 is not a solution. • Check -5. |-5| > 3 True, so the area less than -4 is a solution. • Check 5.
  • 60.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Check 3 numbers. One that solves x > 3, one that solves x < 3, and one that neither inequality. • Check 0 first. Why zero? Because it’s easy. ☺ |0| > 3 False, so the area between -4 and 4 is not a solution. • Check -5. |-5| > 3 True, so the area less than -4 is a solution. • Check 5. |5| > 3 True, so the area greater than 4 is a solution.
  • 61.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 62.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Because a number worked from both inequalities, the solution is an union.
  • 63.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Because a number worked from both inequalities, the solution is an union. • The solution can be written as
  • 64.
    Example 5 (con’t):|x| > 3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • Because a number worked from both inequalities, the solution is an union. • The solution can be written as {x | x < -3 ∪ x > 3}
  • 65.
    Example 6: Whatabout |x| < -3?
  • 66.
    Example 6: Whatabout |x| < -3? Write the inequalities for the 2 cases and solve.
  • 67.
    Example 6: Whatabout |x| < -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case
  • 68.
    Example 6: Whatabout |x| < -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x < -3 -(x) < -3
  • 69.
    Example 6: Whatabout |x| < -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x < -3 -(x) < -3 x>3
  • 70.
    Example 6: Whatabout |x| < -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x < -3 -(x) < -3 x>3 • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 71.
    Example 6: Whatabout |x| < -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x < -3 -(x) < -3 x>3 • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 72.
    Example 6: Whatabout |x| < -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x < -3 -(x) < -3 x>3 • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 73.
    Example 6 (con’t):|x| < -3 -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 74.
    Example 6 (con’t):|x| < -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • It looks a lot like Example 5 so far. Time for our check. Let’s check -4 first.
  • 75.
    Example 6 (con’t):|x| < -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • It looks a lot like Example 5 so far. Time for our check. Let’s check -4 first. ? − ( −4 ) <− 3 4 < −3 4 < −3
  • 76.
    Example 6 (con’t):|x| < -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • It looks a lot like Example 5 so far. Time for our check. Let’s check -4 first. ? − ( −4 ) <− 3 • What?! This isn’t true! 4 < −3 4 < −3
  • 77.
    Example 6 (con’t):|x| < -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • It looks a lot like Example 5 so far. Time for our check. Let’s check -4 first. ? − ( −4 ) <− 3 • What?! This isn’t true! 4 < −3 • Absolute Value is distance. Distance is 4 < −3 never negative. The Absolute Value can never result in a negative number.
  • 78.
    Example 6 (con’t):|x| < -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • It looks a lot like Example 5 so far. Time for our check. Let’s check -4 first. ? − ( −4 ) <− 3 • What?! This isn’t true! 4 < −3 • Absolute Value is distance. Distance is 4 < −3 never negative. The Absolute Value can never result in a negative number. No Solution
  • 79.
    Example 7: Whatabout |x| > -3?
  • 80.
    Example 7: Whatabout |x| > -3? Write the inequalities for the 2 cases and solve.
  • 81.
    Example 7: Whatabout |x| > -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case
  • 82.
    Example 7: Whatabout |x| > -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x > -3 -(x) > -3
  • 83.
    Example 7: Whatabout |x| > -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x > -3 -(x) > -3 x<3
  • 84.
    Example 7: Whatabout |x| > -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x > -3 -(x) > -3 x<3 • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 85.
    Example 7: Whatabout |x| > -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x > -3 -(x) > -3 x<3 • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 86.
    Example 7: Whatabout |x| > -3? Write the inequalities for the 2 cases and solve. Positive Case Negative Case x > -3 -(x) > -3 x<3 • Graph. -5 -4 -3 -2 -1 0 1 2 3 4 5
  • 87.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph?
  • 88.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph? • Check 0.
  • 89.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph? ? 0 >− 3 • Check 0. 0 > −3
  • 90.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph? ? 0 >− 3 • Check 0. 0 > −3 • Looks good. Try -5.
  • 91.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph? ? 0 >− 3 • Check 0. 0 > −3 ? −5 >− 3 • Looks good. Try -5. 5 > −3
  • 92.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph? ? 0 >− 3 • Check 0. 0 > −3 ? −5 >− 3 • Looks good. Try -5. 5 > −3 • Also looks good.
  • 93.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph? ? 0 >− 3 • Check 0. 0 > −3 ? −5 >− 3 • Looks good. Try -5. 5 > −3 • Also looks good. • Is there a number that will not work in the original problem?
  • 94.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph? ? 0 >− 3 • Check 0. 0 > −3 ? −5 >− 3 • Looks good. Try -5. 5 > −3 • Also looks good. • Is there a number that will not work in the original problem? • No, which means the solution can be any real number.
  • 95.
    Example 7 (con’t):|x| > -3 -5 -4 -3 -2 -1 0 1 2 3 4 5 • What is different about the graph? ? 0 >− 3 • Check 0. 0 > −3 ? −5 >− 3 • Looks good. Try -5. 5 > −3 • Also looks good. • Is there a number that will not work in the original problem? • No, which means the solution can be any real number. All Real Numbers