Math Problem Statement

Suppose that f(2) = 6 and that f'(x) <= 5 for all values of x. How large can f(6) possibly be?

Solution

To solve this problem, we need to estimate the maximum possible value of f(6)f(6) given the following information:

  1. f(2)=6f(2) = 6.
  2. The derivative f(x)5f'(x) \leq 5 for all values of xx.

The key concept here is to use the Mean Value Theorem (MVT), which states that for a continuous function ff on the interval [a,b][a, b] that is differentiable on (a,b)(a, b), there exists a point cc in (a,b)(a, b) such that f(c)=f(b)f(a)ba.f'(c) = \frac{f(b) - f(a)}{b - a}.

Step-by-Step Solution

We want to determine the maximum possible value of f(6)f(6), starting from f(2)=6f(2) = 6.

  1. Apply MVT over the interval [2,6][2, 6]: By the Mean Value Theorem, there exists a point cc in (2,6)(2, 6) such that f(c)=f(6)f(2)62.f'(c) = \frac{f(6) - f(2)}{6 - 2}.

  2. Substitute known values: Since f(2)=6f(2) = 6, we get f(c)=f(6)64.f'(c) = \frac{f(6) - 6}{4}.

  3. Use the derivative constraint f(x)5f'(x) \leq 5: Since f(x)5f'(x) \leq 5 for all xx, we can assume f(c)5f'(c) \leq 5. Thus, f(6)645.\frac{f(6) - 6}{4} \leq 5.

  4. Solve for f(6)f(6): Multiply both sides by 4 to obtain f(6)620.f(6) - 6 \leq 20. Adding 6 to both sides, we find f(6)26.f(6) \leq 26.

Conclusion

The largest possible value of f(6)f(6) is 26.

Would you like more details on any step, or do you have further questions?


Related Questions:

  1. How would the answer change if f(x)3f'(x) \leq 3 instead of f(x)5f'(x) \leq 5?
  2. Can the Mean Value Theorem be used if f(x)f(x) is not differentiable on (2,6)(2,6)?
  3. What if we knew f(2)=6f(2) = 6 and f(4)=16f(4) = 16? Could we find f(x)f'(x) for some xx?
  4. How does the Mean Value Theorem help in real-world applications?
  5. How does the assumption of f(x)5f'(x) \leq 5 affect the function's behavior on the interval?

Tip:

The Mean Value Theorem is a powerful tool to understand how much a function can change over an interval when there are constraints on its derivative.

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Math Problem Analysis

Mathematical Concepts

Calculus
Mean Value Theorem
Differentiation

Formulas

Mean Value Theorem: f'(c) = (f(b) - f(a)) / (b - a)

Theorems

Mean Value Theorem

Suitable Grade Level

College Calculus