FUNCTIONS
GRAPHS OF FUNCTIONS; PIECEWISE
DEFINED FUNCTIONS; ABSOLUTE VALUE
FUNCTION; GREATEST INTEGER FUNCTION
 OBJECTIVES:
•  sketch the graph of a function;
•  determine the domain and range  of a 
    function from its graph; and
•  identify whether a relation is a function or 
    not from its graph.
•  define piecewise defined functions;
•  evaluate piecewise defined functions;
•  define absolute value function; and 
•  define greatest integer function
     As we mentioned in our previous lesson, a function 
can be represented in different ways and one of 
which 
is through a graph or its geometric representation. 
We also mentioned that a function may be 
represented as the set of ordered pairs (x, y).  That is 
plotting the set of ordered pairs as points on the 
rectangular coordinates system and joining them will 
determine a curve called the graph of the function.
The graph of a function f consists of all points (x, y) 
whose coordinates satisfy y = f(x), for all x in the 
domain of f.  The set of ordered pairs (x, y) may also 
be represented by (x, f(x)) since y = f(x). 
     Knowledge of the standard forms of the special 
curves discussed in Analytic Geometry such as lines 
and  conic  sections  is  very  helpful  in  sketching  the 
graph  of  a  function.  Functions  other  than  these 
curves can be graphed by point-plotting.
To facilitate the graphing of a function, the 
following steps are suggested:
•  Choose suitable values of x from the domain of a 
    function and 
•  Construct a table of function values y = f(x) from the 
    given values of x.
•  Plot these points (x, y) from the table.
•  Connect the plotted points with a smooth curve.
1
23
)(.4
4)(.3
9)(.2
)(.1
2
2
2
+
++
=
+=
−=
=
x
xx
xh
xxG
xxG
xxf
A. Sketch the graph of the following functions and 
    determine the domain and range.
EXAMPLE:
23)(.6
9)(.5 2
++=
−=
xxg
xxh
SOLUTIONS:
(-3, 0) (3, 0)
(0, 3)
(-2, 3)
(9, 0)
(0, 4)
(-1, 1)
2
)(.1 xxf = xxF −= 9)(.2 4)(.3 2
+= xxG
1
23
)(.4
2
+
++
=
x
xx
xh
2
9)(.5 xxh −=
23)(.6 ++= xxg
( )
[ )+∞
+∞∞−
,0:
,:
R
D
( )
[ )+∞
+∞−
,0:
9,:
R
D ( )
[ )+∞+
+∞∞−
,4:
,:
R
D
( )
( ) 1,:
1,:
++∞∞−
−+∞∞−
exceptR
exceptD [ ]
[ ]3,0:R
3,3:D
+
+−
( )
[ )+∞+
+∞∞−
,3:
,:
R
D
When the graph of a function is given, one can
easily determine its domain and range.
Geometrically, the domain and range of a function
refer to all the x-coordinate and y-coordinate for
which the curve passes, respectively.
Recall that all relations are not functions. A
function is one that has a unique value of the
dependent variable for each value of the
independent variable in its domain. Geometrically
speaking, this means:
Consider the relation defined as {(x, y)|x2
+ y2
= 9}.
When graphed, a circle is formed with center at
(0, 0) having a radius of 3 units. It is not a function
because for any x in the interval (-3, 3), two ordered
pairs have x as their first element. For example, both
(0, 3) and (0, -3) are elements of the relation. Using
the vertical line test, a vertical line when drawn
within –3 ≤ x ≤ 3 intersects the curve at two points.
Refer to the figure below.
A relation f is said to be a function if and only if, in its
graph, each vertical line cuts or touches the curve
at no more than one point.
This is called the vertical line test.
(0, 3)
(3, 0)(-3, 0)
(0, -3)
DEFINITION: PIECEWISE DEFINED FUNCTION
if x<0



+
=
1x
x
)x(f.1
2
0x ≥if
A piecewise defined function is defined by different
formulas on different parts of its domain.
Example:





−
−
−
=
3x
x9
x
)x(f.2 2
0x ≤
1x >
3x0 ≤<
if
if
if
Sometimes a function is defined by more than
one rule or by different formulas. This function is
called a piecewise define function.
if x<0
f(-2), f(-1), f(0), f(1), f(2)
A. Evaluate the piecewise function at the
indicated values.



+
=
1x
x
)x(f.1
2
0x ≥if





−
+=
2
)2x(
1x
x3
)x(f.2
f(-5), f(0), f(1),
f(5)
0x <if
if
if
2x0 ≤≤
2x >
EXAMPLE:
B. Define g(x) = |x| as a piecewise defined
function and evaluate g(-2), g(0) and g(2).
EXAMPLE:
Solution:
From the definition of |x|,



<
≥
−
=
0x
0x
if
if
x
x
)x(g
2)2(g
0)0(g
2)2()2(g
Therefore
=
=
=−−=−
Sketch the graph of the following functions and
determine the domain and range.
EXAMPLE:


 −
=





−
=
2
23
)(.2
3
2
4
)(.1
x
x
xf
xg
if
if
if
1
21
2
−<
<≤−
≥
x
x
x
if
if
1
1
≥
<
x
x



>+
≤
=
112
1
)(.3
2
xifx
xifx
xf
DEFINITION: ABSOLUTE VALUE FUNCTION
Recall that the absolute value or magnitude of
a real number is defined by
Properties of absolute value:



<−
≥
=
0,
0,
xifx
xifx
x
yineaqualittriangleThebaba.4
valuesabsolutetheofratiotheisratioaofvalueabsoluteThe0b,
b
a
b
a
.3
valuesabsolutetheofproducttheisproductaofvalueabsoluteThebaab.2
valueabsolutesamethehavenegativeitsandnumberAaa.1
+≤+
≠=
=
=−
The graph of the function can be obtained
by graphing the two parts of the equation
separately. Combining the two parts produces the V-shaped
graph. It may help to generate the graph of absolute value
function by expressing the function without using absolute
values.
xxf =)(



<−
≥
=
0if,
0if,
xx
xx
y
Example:
Sketch the graph of the following functions and determine
the domain and range.
5x23)x(f.2
1x3x)x(f.1
++=
++=
DEFINITION: GREATEST INTEGER FUNCTION
greatest integer less than or equal to x
The greatest integer function is defined by
  =x
Example:
  =0
  =1.0
  =3.0
  =9.0
  =1
  =1.1
  =2.1
  =9.1
  =2
  =1.2
  =4.3
  =− 4.3
  =− 9.0
0
0
0
0
1
1
1
1
2
2
3
-4
-1
Graph of greatest integer function.
 xy =Sketch the graph of
x  xy =
1x2 −<≤−
0x1 <≤−
1x0 <≤
2x1 <≤
3x2 <≤
2−
1−
0
1
2





x
y
o


EXERCISES:
22
2
2
4:.6
1
12
:.5
3:.4
21:.3
1:.2
34:.1
xyh
x
xx
yg
xyh
xyG
xyF
xyH
+=
−
+−
=
+=
−=
+=
+=
( )( )
( )( )312
943
.10
4:.9
23
211
13
:.8
312
31
:.7
2
22
+−+
−−+
=
−=








≥
<<−
≤−
=





≥+
<−
=
xxx
xxx
y
xyG
xif
xif
xif
yf
xifx
xifx
yF
A. Given the following functions, determine the domain and
range, and sketch the graph:
EXERCISES:
B.Compute the indicated values of the given functions.
4t
4t4
4t
if
if
if
t
1t
3
)x(f
>
≤≤−
−<





+=
)16(andf),4(f),6(f −−
a.





<
≤≤−
−<
−
−
=
x2
2x2
2x
if
if
if
3
1
4
)x(hb.
c.
)2(hand),e(h,
2
h),2(h),3(h 2





 π
−−



−=
−≠
−
−
=
3x
3x
if
if
2
4x
)x(F
2






−−
3
2
Fand),3(F),0(F),4(F
C. Define H(x) as a piecewise defined function and
evaluate H(1), H(2), H(3), H(0) and H(-2) given by,
H(x) = x - |x – 2|.

L2 graphs piecewise, absolute,and greatest integer