Math Problem Statement

Find the average rate of change of the function f(x) = 4 / (-3x - 3) on the interval from x = -4 to x = 4.

Solution

The problem asks to find the average rate of change of the function:

f(x)=43x3f(x) = \frac{4}{-3x - 3}

on the interval x=4x = -4 to x=4x = 4.

The average rate of change of a function f(x)f(x) on an interval [a,b][a, b] is given by:

f(b)f(a)ba\frac{f(b) - f(a)}{b - a}

In this case, a=4a = -4 and b=4b = 4.

Step 1: Calculate f(a)f(a), where a=4a = -4:

f(4)=43(4)3=4123=49f(-4) = \frac{4}{-3(-4) - 3} = \frac{4}{12 - 3} = \frac{4}{9}

Step 2: Calculate f(b)f(b), where b=4b = 4:

f(4)=43(4)3=4123=415=415f(4) = \frac{4}{-3(4) - 3} = \frac{4}{-12 - 3} = \frac{4}{-15} = -\frac{4}{15}

Step 3: Apply the formula for average rate of change:

Average rate of change=f(4)f(4)4(4)=415494+4\text{Average rate of change} = \frac{f(4) - f(-4)}{4 - (-4)} = \frac{-\frac{4}{15} - \frac{4}{9}}{4 + 4}

Simplifying the numerator:

41549=(415+49)-\frac{4}{15} - \frac{4}{9} = -\left(\frac{4}{15} + \frac{4}{9}\right)

Find a common denominator:

415+49=4×345+4×545=1245+2045=3245\frac{4}{15} + \frac{4}{9} = \frac{4 \times 3}{45} + \frac{4 \times 5}{45} = \frac{12}{45} + \frac{20}{45} = \frac{32}{45}

Thus:

41549=3245-\frac{4}{15} - \frac{4}{9} = -\frac{32}{45}

Now divide by 8 (since 4(4)=84 - (-4) = 8):

Average rate of change=32458=3245×18=32360=890=445\text{Average rate of change} = \frac{-\frac{32}{45}}{8} = -\frac{32}{45} \times \frac{1}{8} = -\frac{32}{360} = -\frac{8}{90} = -\frac{4}{45}

So, the average rate of change of the function on the interval [4,4][-4, 4] is:

445-\frac{4}{45}

Let me know if you would like further details or clarification!


Here are 5 related questions:

  1. What is the average rate of change of a linear function?
  2. How do you interpret the result of the average rate of change in real-world problems?
  3. How is the average rate of change different from the instantaneous rate of change?
  4. Can the average rate of change be zero for non-constant functions?
  5. How does the sign of the average rate of change inform us about the behavior of the function?

Tip: To find the average rate of change of a function, think of it as finding the slope of the secant line between two points on the curve!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Functions
Rates of Change

Formulas

Average rate of change formula: (f(b) - f(a)) / (b - a)

Theorems

Slope of a Secant Line

Suitable Grade Level

Grades 9-12