Page 58 - Math Course 1 (Book 2)

Relations as a Function

Equations as Functions
Read the Test Item The independent variable
Example is d and the dependent
variable is m.

Solve the Test Item
Determine whether x = –2 is a function.
Choice A represents the function
Graph the equation. Since the graph is in the form m = 3.5d. This is incorrect
Ax + By = C, the graph of the equation will be a line. because it should be
m = 5d
Place your pencil at the left of the graph to represent
a vertical line. Slowly move the pencil to the right Choices B and C represent the function
1
across the graph. m= d,
5
which is incorrect
At x = –2 this vertical line passes through more than
one point on the graph. In Choice D the graph represents the
function m = 5d, which is
correct.

Answer The answer is D.

Your Turn!

Identify Functions

A. Is this relation a function? Explain.

The graph does not pass the
Answer vertical line test. Thus, the line
does not represent a function.

Standardized Test Example A. Yes; for each element of the domain, there is only
one corresponding element in the range.
Example B. Yes; because it can be represented by a mapping.

The algebraic form of a function is m = 5d, where C. No; because it has negative x-values.
d is the number of dollars customers of Mike’s Car
Rental donate to a charity and m is the donation D. No; because both –2 and 2 are in the range.
made by Mike’s Car Rental. Which of the following
represents the same function? Answer

A. For every $2 dollars donated, B. f (d) = 5m
Mike’s Car Rental donates $7.
x y
C. 0 00 D.
10 2
60 12
50