How would the equation y = 3x − 12 be expressed in function notation?

A. f(x) = 3x − 12
Correct! f(x) is one way to use function notation for y.

B. f(x) = 3f(x) − 12
Incorrect. f(x) replaces y and the expression on the right of the equal sign stays the same.

C. f(x) = 3 − 12x
Incorrect. f(x) replaces y and the expression on the right of the equal sign stays the same.

D. f = 3x − 12
Incorrect. Function notation should have x, the input, in parenthesis next to f, the name of the function.

Jessica’s monthly cell phone bill includes a $5.00 monthly fee and $0.10 for every minute she uses her phone. Write an equation that expresses f, Jessica’s monthly cell phone bill as a function of m, the number of minutes she talks on the phone?

A. f(m) = 0.10 + 5
Incorrect. Remember this is a function of m, the number of minutes, so m should be part of the equation.

B. f(m) = 0.10m + 5
Correct! The number of minutes, m, is multiplied by $0.10 and the $5 monthly fee is added on.

C. f(m) = 0.10 + 5m
Incorrect. m, the number of minutes should be multiplied by the cost per minute.

D. f(m) = 0.10m + 5m
Incorrect. The number of minutes, m, should only be multiplied by the cost per minute.

Julio needs 2 fence boards for each foot of fencing he builds; he also needs 10 fence boards for a gate at the end of the fence. Which equation shows the total number of fence boards needed,  f, as a function of the length of the fence in feet, n?

A. f(n) = 2n + 10
Correct! The length of the fence in feet, n, is multiplied by the number of fence boards for each foot and the number of boards for the gate is added on.

B. f(n) = 2n + 10n
Incorrect. The length of the fence in feet, n, should only be multiplied by the number of fence boards for each foot.

C. f(n) = 2 + 10n
Incorrect. The length of the fence boards in feet, n, should be multiplied by the number of fence boards for each foot.

D. f(n) = 2 + 10
Incorrect. The length of the fence boards in feet, n, should be multiplied by the number of fence boards for each foot.

The cost of purchasing T-shirts for the drama club is represented by f(x) = $2.50x + $15, where x is the number of shirts purchased. How much will the drama club pay for 20 T-shirts?

A. $20
Incorrect. Multiply the number of T-shirts by the cost of each T-shirt then add $15.

B. $300
Incorrect. Multiply the number of T-shirts by the cost of each T-shirt then add $15.

C. $55
Incorrect. Multiply the number of T-shirts by the cost of each T-shirt then add $15.

D. $65
Correct! You substituted 20 for x and computed correctly.

A local electrician uses the following function to calculate his earnings for each hour of a job, x. f(x) = $35x + $50. If he earned a total of $155, f(x) = $155, how many hours, x, was he at this job?

A. 2
Incorrect. Substitute $155 for f(x), then solve the equation for the number of hours, x.

B. 3
Correct! you substituted $155 for f(x), then solved the equation for the number of hours, x.

C. 4
Incorrect. Substitute $155 for f(x), then solve the equation for the number of hours, x.

D. 5
Incorrect. Substitute $155 for f(x), then solve the equation for the number of hours, x.