Question #1866

Suppose that f(x) is continuous and differentiable on the interval [2,5]. Suppose also that f(2) = 9 and f’(x) ≤9. What is the largest possible value for f(5)?

Expert's answer

We'll try to use the definition of the derivative:

f'(x) = (f(b) - f(a))/(b-a))

thus

(f(5) - f(2))/(5-2) = (f(5) - 9) /3 ≤ 9.

(f(5) - 9) ≤ 27

f(5) ≤ 36.

Answer: 36.

f'(x) = (f(b) - f(a))/(b-a))

thus

(f(5) - f(2))/(5-2) = (f(5) - 9) /3 ≤ 9.

(f(5) - 9) ≤ 27

f(5) ≤ 36.

Answer: 36.

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