Function notation: read and evaluate f(x), including f(x + 2) and f(2x)

Answer Key - Grade 9 Math Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Bo's robot builds a tower. The tower has f(m) = 4m + 12 blocks after m minutes. What is f(15)?

   72
2. 2.

   Esme's game gives stars. The score is f(r) = 7r − 9 after r rounds. What is f(6)?

   33
3. 3.

   Jun rides a school bus. The riders on board are f(s) = 3s + 7 after s stops. What is f(12)?

   43
4. 4.

   Kira's number machine follows f(x) = x² + 2x − 4. Kira feeds in −3. What is f(−3)?

   -1
5. 5.

   Luz invents a number game: f(x) = x² − 3x + 1. Luz tries the input −5. What is f(−5)?

   41
6. 6.

   Milo's calculator follows f(x) = x² + 2x + 5. Milo types in −4. What is f(−4)?

   13
7. 7.

   Noah sells cookies. The function c(n) gives the cost in dollars of n cookies, and c(5) = 12. What does c(5) = 12 tell us?

   • 5 cookies cost $12
   • 12 cookies cost $5
   • Each cookie costs $12
8. 8.

   Ren watches a bus on a trip. The function d(t) gives the miles it has gone after t hours, and d(4) = 220. What does d(4) = 220 tell us?

   • The bus goes 220 miles each hour
   • After 220 hours, the bus has gone 4 miles
   • After 4 hours, the bus has gone 220 miles
9. 9.

   Zee's snack cart follows f(x) = 3x − 4 for the dollars earned after x sales. For which x does f(x) = 23?

   9
10. 10.

    Ari's sharpening game follows f(x) = 4x − 6 for the points after x pencils. For which x does f(x) = 42?

    12