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.

   Ari's toy rocket climbs. Its height is f(s) = 6s − 4 meters after s seconds. What is f(7)?

   38
2. 2.

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

   72
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.

   Pia's plant is growing. The function h(w) gives its height in cm after w weeks, and h(6) = 30. What does h(6) = 30 tell us?

   • After 30 weeks, the plant is 6 cm tall
   • The plant grows 30 cm each week
   • After 6 weeks, the plant is 30 cm tall
8. 8.

   Tala bounces a ball (it has a squeaky voice). The rule f(x) = 2x + 9 gives the points scored. For which x does f(x) = 25?

   8
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