1. Objectives 1. To determine if a relation is a function.
2. To find the value of a function.

2. Functions
A function is a relation in which each element of the domain is paired with exactly one element of the range. Another way of saying it is that there is one and only one output (y) with each input (x).
f(x) x y

3. Function Notation
Input
Name of Function
Output

4. Determine whether each relation is a function.
1. {(2, 3), (3, 0), (5, 2), (4, 3)}
YES, every domain is different!
f(x) 2 3
f(x) 3
f(x) 5 2
f(x) 4 3

5. Identify the Domain and Range. Then tell if the relation is a function.
Input Output 4
Notice the set notation!!!
Domain = {-3, 1,4}
Range = {3,-2,1,4}
Function?
No: input 1 is mapped onto
Both -2 & 1

6. Identify the Domain and Range. Then tell if the relation is a function.
Input Output 4
Function?
Yes: each input is mapped
onto exactly one output
Domain = {-3, 1,3,4}
Range = {3,1,-2}

7. A Relation can be represented by a set of ordered pairs of the form (x,y)
Quadrant II
X<0, y>0
Quadrant I
X>0, y>0
Origin (0,0)
Quadrant IV
X>0, y<0
Quadrant III
X<0, y<0

8. Graphing Relations To graph the relation in the previous example:
Write as ordered pairs (-3,3), (1,-2), (1,1), (4,4)
Plot the points

9. (-3,3)
(4,4)
(1,1)
(1,-2)

10. Same with the points (-3,3), (1,1), (3,1), (4,-2)

11. (-3,3)
(1,1)
(3,1)
(4,-2)

12. Vertical Line Test
You can use the vertical line test to visually determine if a relation is a function.
Slide any vertical line (pencil) across the graph to see if any two points lie on the same vertical line.
If there are not two points on the same vertical line then the relation is a function.
If there are two points on the same vertical line then the relation is NOT a function

13. Use the vertical line test to visually check if the relation is a function.
(-3,3)
(4,4)
(1,1)
(1,-2)
Function?
No, Two points are on
The same vertical line.

14. Use the vertical line test to visually check if the relation is a function.
(-3,3)
(1,1)
(3,1)
(4,-2)
Function?
Yes, no two points are
on the same vertical line

15. Determine whether the relation is a function.
2. {(4, 1), (5, 2), (5, 3), (6, 6), (1, 9)}
f(x) 4 1
f(x) 5 2
NO, 5 is paired with 2 numbers!
f(x) 5 3
f(x) 6
f(x) 1 9

16. Is this relation a function? {(1,3), (2,3), (3,3)}
Yes No
Answer Now

17. Vertical Line Test (pencil test)
If any vertical line passes through more than one point of the graph, then that relation is not a function. Are these functions?
FUNCTION!
FUNCTION!
NO!

18. Vertical Line Test
FUNCTION!
NO!
NO!
FUNCTION!

19. Is this a graph of a function?
Yes No
Answer Now

20. 3(3)-2 3 7 -8 -2 3(-2)-2 1) f(3) 2) f(-2) = 7 = -8
Given f(x) = 3x - 2, find:
1) f(3) 2) f(-2)
= 7
3(3)-2 3 7
= -8
3(-2)-2 -2 -8

21. Given h(z) = z2 - 4z + 9, find h(-3)
(-3)2-4(-3)+9 -3 30
h(-3) = 30

22. Given g(x) = x2 – 2, find g(4) 2 6 14 18
Answer Now