Math Problem Statement

Consider the function f(x)=1−2x2f(x)=1-2x2 on the interval [−5,3][-5,3]. Find the average or mean slope of the function on this interval, i.e. f(3)−f(−5)3−(−5)=f(3)-f(-5)3-(-5)=   

By the Mean Value Theorem, we know there exists a cc in the open interval (−5,3)(-5,3) such that f'(c)f′(c) is equal to this mean slope. For this problem, there is only one cc that works. Find it.   

Solution

To solve this problem, we need to follow these steps:

Step 1: Calculate the Mean Slope of f(x)f(x) on the Interval [5,3][-5, 3]

The mean (or average) slope of f(x)f(x) on the interval [5,3][-5, 3] is given by: f(3)f(5)3(5)\frac{f(3) - f(-5)}{3 - (-5)} The function is: f(x)=12x2f(x) = 1 - 2x^2

Calculate f(3)f(3) and f(5)f(-5):

  1. f(3)=12(3)2=118=17f(3) = 1 - 2(3)^2 = 1 - 18 = -17
  2. f(5)=12(5)2=12×25=150=49f(-5) = 1 - 2(-5)^2 = 1 - 2 \times 25 = 1 - 50 = -49

Substitute these values into the mean slope formula:

f(3)f(5)3(5)=17(49)3+5=17+498=328=4\frac{f(3) - f(-5)}{3 - (-5)} = \frac{-17 - (-49)}{3 + 5} = \frac{-17 + 49}{8} = \frac{32}{8} = 4

So, the mean slope is 44.

Step 2: Apply the Mean Value Theorem (MVT)

According to the Mean Value Theorem, there exists a point cc in the interval (5,3)(-5, 3) such that f(c)f'(c) is equal to this mean slope.

  1. Find f(x)f'(x): Differentiate f(x)=12x2f(x) = 1 - 2x^2: f(x)=4xf'(x) = -4x

  2. Set f(c)=4f'(c) = 4 and solve for cc: 4c=4-4c = 4 c=1c = -1

Conclusion

The point cc that satisfies the Mean Value Theorem is c=1c = -1.

Final Answer

  • Mean slope of f(x)f(x) on [5,3][-5, 3]: 44
  • Value of cc where f(c)=4f'(c) = 4: c=1c = -1

Would you like further details on any part of this solution?


Here are some related questions:

  1. What would happen if the interval were changed, say to [4,2][-4, 2]?
  2. How does the Mean Value Theorem apply to other types of functions, like trigonometric ones?
  3. Can the Mean Value Theorem have more than one solution cc in an interval?
  4. How do we interpret the Mean Value Theorem geometrically on a graph?
  5. What are other key theorems related to derivatives and slopes?

Tip: In calculus, the Mean Value Theorem not only helps find average slopes but also guarantees at least one point where the instantaneous rate of change equals the average rate over an interval.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Calculus
Functions
Mean Slope
Differentiation

Formulas

Mean Slope Formula: (f(b) - f(a)) / (b - a)
Derivative of f(x): f'(x)

Theorems

Mean Value Theorem

Suitable Grade Level

Grades 11-12