Page 59 - Math Course 1 (Book 2)

Relations as a Function

Identify Functions
MO. 8 - L6b
B. Is this relation a function? Explain.
x y Finding Functional Values
3 2
1 –2
2 –4 Vocabulary A-Z
3 –1 Let us learn some vocabulary

A. No; because the element 3 in the domain is
paired with both 2 and –1 in the range.

function notation
B. No; because there are negative values in the
range. Equations that are functions can be written in a
form called function notation.
C. Yes; because it is a line when graphed.
For example, consider y = 3x – 8.
D. Yes; because it can be represented in a chart.
Equation Function notation
Answer y = 3x – 8 f(x) = 3x – 8

Equations as Functions In a function, x represents the independent
quantity, or the elements of the domain and f(x)
Determine whether 3x + 2y = 12 is a function. represents the dependent quantity, or the elements
of the range.
A. yes
B. no function value
C. not enough
information In a function, x represents the independent
quantity, or the elements of the domain and f(x)
represents the dependent quantity, or the elements
of the range.

f(5) is the element in the range that corresponds to
the element 5 in the domain. We say that f(5) is the
Answer function value of f for x = 5.

Standardized Test Example f(x) = 2x + 5

The algebraic form of a function is c = 5h, where h f(–2) function value
of f for x = –2
is the number of hours a pool is rented and c is the
replace
cost to the PTA. Which of the following represents f(–2) = 2(–2) + 5 x with –2
the same function?
= –4 + 5 Multiply
A. f (h) = 5c
= 1 Add.
B. For every two hours the pool is rented, the cost
to the PTA is $10.
f(1) + 4 function value
C. f (h) = 2c of f for x = 1
f(1) + 4 = [2(1) + 5] + 4 replace
D. For every two hours the pool is rented, the x = 1
cost to the PTA is $5.
= 7 + 4 Simplify.
Answer
= 11 Add.

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