Evaluate and graph an exponential function

Answer Key - Grade 9 Math Worksheet - Building Confidence

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

1. 1.

   Kira's math-club function machine uses f(x) = 7 · 3^x. Any nonzero number to the power zero is 1. What is the y-intercept, the output when the input is zero?

   7
2. 2.

   Luz's video game gives f(x) = 5 · 4^x coins on level x. Any nonzero number to the power zero is 1. What is the y-intercept, the output when the input is zero?

   5
3. 3.

   Milo's science notes say f(x) = 12 · 2^x bacteria after x hours. Any nonzero number to the power zero is 1. What is the y-intercept, the output when the input is zero?

   12
4. 4.

   Noah's block-pattern game uses f(x) = 9 · 5^x. Any nonzero number to the power zero is 1. What is the y-intercept, the output when the input is zero?

   9
5. 5.

   0 | 5; 1 | 10; 2 | ?; 3 | ?. Every arrow down the table: × 2. Pia's plant-cutting rule is f(x) = 5 · 2^x. The growth table starts at 5, and every arrow is × 2. What is f(3)?

   40
6. 6.

   0 | 2; 1 | 10; 2 | ?; 3 | ?. Every arrow down the table: × 5. Tala's flower-pattern rule is f(x) = 2 · 5^x. The growth table starts at 2, and every arrow is × 5. What is f(3)?

   250

7. Read this first

   Growth table (x | f(x))

   0 | 4; 1 | 8; 2 | ?; 3 | ?; 4 | ?; 5 | ?. Every arrow down the table: × 2.

8. 7.

   Zee's paper-folding rule is f(x) = 4 · 2^x. The growth table starts at 4, and every arrow is × 2. What is f(5)?

   128

9. Growth table

   x	f(x)
   -2	?
   -1	?
   0	32
   1	64

   Arrow down: × 2. Arrow up: ÷ 2.

10. 8.

    Ari's rule for a bucket game is f(x) = 32 · 2^x. Going up one row in the growth table divides by 2. What is f(-2)?

    8
11. 9.

    Bo's drum-beat rule is f(x) = 40 · 2^x. Going up one row in the growth table divides by 2. What is f(-3)?

    5
12. 10.

    Arrow down: × 3. Arrow up: ÷ 3. Esme's kite-club rule is f(x) = 81 · 3^x. Going up one row in the growth table divides by 3. What is f(-2)?

    9