Math Problem Statement

Find the relative extreme points of the​ function, if they exist. Then sketch a graph of the function. (x-5)^1/3

Solution

To find the relative extreme points of the function f(x)=(x5)1/3f(x) = (x - 5)^{1/3}, we follow these steps:

Step 1: First Derivative

The relative extreme points occur where the derivative f(x)f'(x) is zero or undefined. We start by finding the first derivative of f(x)f(x).

Using the chain rule, we differentiate f(x)=(x5)1/3f(x) = (x - 5)^{1/3}:

f(x)=13(x5)2/3(1)=13(x5)2/3f'(x) = \frac{1}{3}(x - 5)^{-2/3} \cdot (1) = \frac{1}{3}(x - 5)^{-2/3}

Thus, the derivative is:

f(x)=13(x5)2/3f'(x) = \frac{1}{3}(x - 5)^{-2/3}

Step 2: Identify Critical Points

To find critical points, we solve f(x)=0f'(x) = 0 and check where the derivative is undefined.

  1. Where is f(x)=0f'(x) = 0?

For f(x)=0f'(x) = 0, we set:

13(x5)2/3=0\frac{1}{3}(x - 5)^{-2/3} = 0

This equation has no solution because (x5)2/3(x - 5)^{-2/3} is never zero for any real value of xx.

  1. Where is f(x)f'(x) undefined?

The derivative f(x)f'(x) is undefined when x=5x = 5, since the denominator involves (x5)2/3(x - 5)^{-2/3}, which is undefined at x=5x = 5.

Step 3: Second Derivative Test

Let's check if x=5x = 5 is a potential extreme point by analyzing the behavior of the function around this point.

Second Derivative:

We find the second derivative f(x)f''(x) by differentiating f(x)f'(x):

f(x)=13(x5)2/3f'(x) = \frac{1}{3}(x - 5)^{-2/3}

Differentiating this:

f(x)=29(x5)5/3f''(x) = -\frac{2}{9}(x - 5)^{-5/3}

Thus,

f(x)=29(x5)5/3f''(x) = -\frac{2}{9}(x - 5)^{-5/3}

The second derivative shows that the function is undefined at x=5x = 5. To the left of x=5x = 5, the second derivative is positive, and to the right, it is negative. This indicates that the function has a cusp at x=5x = 5 and is not differentiable there.

Step 4: Conclusion

The function has no relative extreme points because the derivative does not become zero at any point. However, there is a cusp at x=5x = 5, indicating a sharp change in the slope but no local maximum or minimum.

Step 5: Graph of the Function

The graph of f(x)=(x5)1/3f(x) = (x - 5)^{1/3} looks like a cube root function, but it is shifted to the right by 5 units. The function is continuous and passes through x=5x = 5 with a cusp. The slope approaches infinity near x=5x = 5, and the function has no relative extrema.

Would you like a visual sketch of this graph?


Here are some related questions to explore:

  1. What is the significance of a cusp in a function's graph?
  2. Can a function have a critical point where it is not differentiable?
  3. What is the geometric meaning of a cube root function?
  4. How does the chain rule apply to functions with fractional exponents?
  5. Why does the derivative become undefined at certain points?

Tip: When a function has a cusp or corner at a point, it indicates that the function is continuous but not smooth at that point.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Critical Points
Cusp

Formulas

f'(x) = (1/3)(x - 5)^(-2/3)
f''(x) = -(2/9)(x - 5)^(-5/3)

Theorems

First Derivative Test
Second Derivative Test

Suitable Grade Level

Grades 11-12