Math Problem Statement

If f and g are functions whose graphs are shown, let u(x) = f(x)g(x) and v(x) = f(x)/g(x). Find u'(1) and v'(5).

Solution

Let's break down the problem shown in the image.

We are given two functions f(x)f(x) and g(x)g(x), and we are tasked with finding:

(a) u(1)u'(1), where u(x)=f(x)g(x)u(x) = f(x) g(x).

(b) v(5)v'(5), where v(x)=f(x)g(x)v(x) = \frac{f(x)}{g(x)}.

Part (a): Finding u(1)u'(1)

For u(x)=f(x)g(x)u(x) = f(x)g(x), we need to apply the product rule: u(x)=f(x)g(x)+f(x)g(x)u'(x) = f'(x)g(x) + f(x)g'(x) At x=1x = 1, we need to find f(1)f(1), f(1)f'(1), g(1)g(1), and g(1)g'(1).

From the graph:

  • f(1)=0f(1) = 0 (since the function f(x)f(x) crosses the x-axis at x=1x = 1),
  • g(1)=0g(1) = 0 (the graph of g(x)g(x) also crosses the x-axis at x=1x = 1),
  • f(1)f'(1), which is the slope of the line at x=1x = 1, is negative (approx. 2-2),
  • g(1)g'(1) is positive (approx. 22).

Using the product rule at x=1x = 1: u(1)=f(1)g(1)+f(1)g(1)=(2)(0)+(0)(2)=0u'(1) = f'(1)g(1) + f(1)g'(1) = (-2)(0) + (0)(2) = 0 So, u(1)=0u'(1) = 0, which is correctly marked in your solution.

Part (b): Finding v(5)v'(5)

For v(x)=f(x)g(x)v(x) = \frac{f(x)}{g(x)}, we need to apply the quotient rule: v(x)=f(x)g(x)f(x)g(x)(g(x))2v'(x) = \frac{f'(x)g(x) - f(x)g'(x)}{(g(x))^2} At x=5x = 5, we need to find f(5)f(5), f(5)f'(5), g(5)g(5), and g(5)g'(5).

From the graph:

  • f(5)=1f(5) = 1,
  • g(5)=2g(5) = -2,
  • f(5)f'(5) (the slope of f(x)f(x) at x=5x = 5) is approximately 0.50.5,
  • g(5)g'(5) (the slope of g(x)g(x) at x=5x = 5) is 11.

Now, applying the quotient rule: v(5)=(0.5)(2)(1)(1)(2)2=114=24=12v'(5) = \frac{(0.5)(-2) - (1)(1)}{(-2)^2} = \frac{-1 - 1}{4} = \frac{-2}{4} = -\frac{1}{2}

Thus, v(5)=12v'(5) = -\frac{1}{2}.

Let me know if you need more details, or have further questions! Here are some related questions for you:

  1. What is the difference between the product rule and quotient rule?
  2. How do you determine the slope of a linear function from a graph?
  3. Can the derivative of a product ever be zero? Why or why not?
  4. How does the sign of the slope affect the behavior of the derivative?
  5. What does a zero derivative tell you about the function at that point?

Tip: Always verify the slopes carefully from the graph when calculating derivatives using product or quotient rules.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Product Rule
Quotient Rule

Formulas

Product Rule: u'(x) = f'(x)g(x) + f(x)g'(x)
Quotient Rule: v'(x) = (f'(x)g(x) - f(x)g'(x)) / (g(x))^2

Theorems

Product Rule
Quotient Rule

Suitable Grade Level

Grades 11-12