Math Problem Statement

Selected values of the function f are shown in the table below. The function f is differentiable on the open interval 1 < x < 7. Determine the validity of the following statement: There exists a value c in the open interval 1 < x < 7 such that f'(c) = -6. The table is provided with x = 1, 4, 7 and corresponding f(x) values -3, -18, -39.

Solution

The problem provided asks to determine the validity of the statement: "There exists a value cc in the open interval 1<x<71 < x < 7 such that f(c)=6f'(c) = -6."

Given the function values in the table, we need to apply the Mean Value Theorem (MVT), which states that if a function ff is continuous on a closed interval [a,b][a, b] and differentiable on the open interval (a,b)(a, b), then there exists at least one cc in (a,b)(a, b) such that:

f(c)=f(b)f(a)baf'(c) = \frac{f(b) - f(a)}{b - a}

Here, the function values are:

  • f(1)=3f(1) = -3
  • f(4)=18f(4) = -18
  • f(7)=39f(7) = -39

We can calculate the slope of the secant line between any two points on the interval [1,7][1, 7] to see if it matches 6-6.

Step 1: Calculate the secant slopes for the interval [1,7][1, 7]

f(7)f(1)71=39(3)71=39+36=366=6\frac{f(7) - f(1)}{7 - 1} = \frac{-39 - (-3)}{7 - 1} = \frac{-39 + 3}{6} = \frac{-36}{6} = -6

Conclusion:

The secant slope between x=1x = 1 and x=7x = 7 is exactly 6-6, and since the function is differentiable on the open interval 1<x<71 < x < 7, by the Mean Value Theorem, there must exist a value cc in (1,7)(1, 7) where f(c)=6f'(c) = -6.

Thus, the statement is true.

Would you like a further breakdown of any of the steps? Feel free to ask.

Related Questions:

  1. How do you apply the Mean Value Theorem to other functions?
  2. What does the concept of differentiability imply for a function?
  3. How do you determine if a function is continuous over an interval?
  4. What is the geometric interpretation of the Mean Value Theorem?
  5. How do you solve for a point cc in the Mean Value Theorem problem?

Tip: Always check the conditions for the Mean Value Theorem: continuity on the closed interval and differentiability on the open interval!

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Math Problem Analysis

Mathematical Concepts

Differentiability
Mean Value Theorem
Rate of Change

Formulas

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

Theorems

Mean Value Theorem

Suitable Grade Level

Grades 10-12