Math Problem Statement

Find the two x-intercepts of the function f(x) = -4√x + 4 and show that f'(x) = 0 at some point between the two x-intercepts.

Solution

Let's break down the problem step by step.

1. Find the x-intercepts of the function f(x)=4x+4f(x) = -4\sqrt{x} + 4:

The x-intercepts are found by setting f(x)=0f(x) = 0 and solving for xx.

f(x)=4x+4=0f(x) = -4\sqrt{x} + 4 = 0

Solving for xx:

4x+4=0-4\sqrt{x} + 4 = 0 Move the constant to the other side: 4x=4-4\sqrt{x} = -4 Divide both sides by -4: x=1\sqrt{x} = 1 Square both sides: x=1x = 1

Thus, the larger x-value is x=1x = 1.

Now, let's look for any additional x-intercepts. However, since square roots only allow non-negative values, the smallest possible x-value is 0. But, substituting x=0x = 0 into the function:

f(0)=40+4=4f(0) = -4\sqrt{0} + 4 = 4

This means x=0x = 0 is not an x-intercept. Hence, the only x-intercept is x=1x = 1.

2. Showing that f(x)=0f'(x) = 0 at some point between the two x-intercepts:

The derivative f(x)f'(x) will help us check where the slope of the function is zero.

First, let's find f(x)f'(x). Recall that the derivative of x\sqrt{x} is: ddx(x)=12x\frac{d}{dx} \left( \sqrt{x} \right) = \frac{1}{2\sqrt{x}}

So, the derivative of f(x)=4x+4f(x) = -4\sqrt{x} + 4 is:

f(x)=4×12x=2xf'(x) = -4 \times \frac{1}{2\sqrt{x}} = -\frac{2}{\sqrt{x}}

Now, set f(x)=0f'(x) = 0:

2x=0-\frac{2}{\sqrt{x}} = 0

This equation has no solution, as the expression cannot equal zero for any real xx. Therefore, f(x)=0f'(x) = 0 does not occur at any point. The solution to f(x)=0f'(x) = 0 seems incorrect.

3. Correct Interpretation:

The question asks for a value of xx such that f(x)=0f'(x) = 0, but no such xx exists. This means the answer provided for that part is incorrect.


Do you want further details or have any questions on this problem?

Here are five related questions:

  1. What happens to the function f(x)f(x) for negative values of xx?
  2. How would the behavior of the function change if it were f(x)=4x+4f(x) = 4\sqrt{x} + 4 instead?
  3. Can a square root function have multiple x-intercepts?
  4. What does the derivative f(x)f'(x) represent in terms of the slope of the graph?
  5. Why does f(x)f'(x) not have a solution for f(x)=0f'(x) = 0?

Tip: When solving for the derivative of a function involving square roots, make sure to simplify carefully and verify whether the derivative can be zero within the domain of the original function.

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Math Problem Analysis

Mathematical Concepts

Algebra
Calculus
Derivatives
Square Roots

Formulas

Square root function f(x) = -4√x + 4
Derivative of f(x) = -4√x + 4

Theorems

Intermediate Value Theorem

Suitable Grade Level

Grades 11-12