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Advanced MathVery hardIdentifying exponential decay from a table

Advanced Math practice question

x: 0, 1, 2, 3 f(x): 96, 48, 24, 12

The table gives values of a function f. Which equation could define f?

  1. A. f(x) = 96(1/2)ˣCorrect
  2. B. f(x) = 96 − 48x
  3. C. f(x) = 96(2)ˣ
  4. D. f(x) = 48(1/2)ˣ

Answer: A. f(x) = 96(1/2)ˣ

Each step halves the value: 96, 48, 24, 12. That's exponential decay with factor 1/2 and starting value 96: f(x) = 96(1/2)ˣ.

Why the other answers are wrong

B. f(x) = 96 − 48x
96 − 48x is linear: it would give 96, 48, 0, −48.
C. f(x) = 96(2)ˣ
96(2)ˣ doubles each step instead of halving.
D. f(x) = 48(1/2)ˣ
48(1/2)ˣ starts at 48, but f(0) = 96.

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