IDNLearn.com is designed to help you find the answers you need quickly and easily. Join our community to receive prompt, thorough responses from knowledgeable experts.
Sagot :
To determine over which interval the function [tex]\( f(x) = x^2 - x - 1 \)[/tex] has an average rate of change of zero, let's analyze each given interval and calculate the average rate of change step-by-step.
The formula for the average rate of change of a function [tex]\( f(x) \)[/tex] over the interval [tex]\([a, b]\)[/tex] is given by:
[tex]\[ \text{Average rate of change} = \frac{f(b) - f(a)}{b - a} \][/tex]
Let's analyze the intervals provided.
### Interval A: [tex]\(-5 \leq x \leq 5\)[/tex]
[tex]\[ a = -5, \quad b = 5 \][/tex]
[tex]\[ f(a) = f(-5) = (-5)^2 - (-5) - 1 = 25 + 5 - 1 = 29 \][/tex]
[tex]\[ f(b) = f(5) = 5^2 - 5 - 1 = 25 - 5 - 1 = 19 \][/tex]
[tex]\[ \text{Average rate of change} = \frac{f(5) - f(-5)}{5 - (-5)} = \frac{19 - 29}{10} = \frac{-10}{10} = -1 \][/tex]
The average rate of change over interval A is [tex]\(-1\)[/tex], which is not zero.
### Interval B: [tex]\(-3 \leq x \leq -2\)[/tex]
[tex]\[ a = -3, \quad b = -2 \][/tex]
[tex]\[ f(a) = f(-3) = (-3)^2 - (-3) - 1 = 9 + 3 - 1 = 11 \][/tex]
[tex]\[ f(b) = f(-2) = (-2)^2 - (-2) - 1 = 4 + 2 - 1 = 5 \][/tex]
[tex]\[ \text{Average rate of change} = \frac{f(-2) - f(-3)}{-2 - (-3)} = \frac{5 - 11}{1} = -6 \][/tex]
The average rate of change over interval B is [tex]\(-6\)[/tex], which is not zero.
### Interval C: [tex]\(-1 \leq x \leq 2\)[/tex]
[tex]\[ a = -1, \quad b = 2 \][/tex]
[tex]\[ f(a) = f(-1) = (-1)^2 - (-1) - 1 = 1 + 1 - 1 = 1 \][/tex]
[tex]\[ f(b) = f(2) = 2^2 - 2 - 1 = 4 - 2 - 1 = 1 \][/tex]
[tex]\[ \text{Average rate of change} = \frac{f(2) - f(-1)}{2 - (-1)} = \frac{1 - 1}{3} = \frac{0}{3} = 0 \][/tex]
The average rate of change over interval C is [tex]\(0\)[/tex], which is exactly what we are looking for.
### Interval D: [tex]\(2 \leq x \leq 3\)[/tex]
[tex]\[ a = 2, \quad b = 3 \][/tex]
[tex]\[ f(a) = f(2) = 2^2 - 2 - 1 = 1 \][/tex]
[tex]\[ f(b) = f(3) = 3^2 - 3 - 1 = 9 - 3 - 1 = 5 \][/tex]
[tex]\[ \text{Average rate of change} = \frac{f(3) - f(2)}{3 - 2} = \frac{5 - 1}{1} = 4 \][/tex]
The average rate of change over interval D is [tex]\(4\)[/tex], which is not zero.
After analyzing all the intervals, we conclude:
The function [tex]\( f(x) = x^2 - x - 1 \)[/tex] has an average rate of change of zero over the interval:
[tex]\[ \boxed{-1 \leq x \leq 2} \][/tex]
So the correct answer is (C).
The formula for the average rate of change of a function [tex]\( f(x) \)[/tex] over the interval [tex]\([a, b]\)[/tex] is given by:
[tex]\[ \text{Average rate of change} = \frac{f(b) - f(a)}{b - a} \][/tex]
Let's analyze the intervals provided.
### Interval A: [tex]\(-5 \leq x \leq 5\)[/tex]
[tex]\[ a = -5, \quad b = 5 \][/tex]
[tex]\[ f(a) = f(-5) = (-5)^2 - (-5) - 1 = 25 + 5 - 1 = 29 \][/tex]
[tex]\[ f(b) = f(5) = 5^2 - 5 - 1 = 25 - 5 - 1 = 19 \][/tex]
[tex]\[ \text{Average rate of change} = \frac{f(5) - f(-5)}{5 - (-5)} = \frac{19 - 29}{10} = \frac{-10}{10} = -1 \][/tex]
The average rate of change over interval A is [tex]\(-1\)[/tex], which is not zero.
### Interval B: [tex]\(-3 \leq x \leq -2\)[/tex]
[tex]\[ a = -3, \quad b = -2 \][/tex]
[tex]\[ f(a) = f(-3) = (-3)^2 - (-3) - 1 = 9 + 3 - 1 = 11 \][/tex]
[tex]\[ f(b) = f(-2) = (-2)^2 - (-2) - 1 = 4 + 2 - 1 = 5 \][/tex]
[tex]\[ \text{Average rate of change} = \frac{f(-2) - f(-3)}{-2 - (-3)} = \frac{5 - 11}{1} = -6 \][/tex]
The average rate of change over interval B is [tex]\(-6\)[/tex], which is not zero.
### Interval C: [tex]\(-1 \leq x \leq 2\)[/tex]
[tex]\[ a = -1, \quad b = 2 \][/tex]
[tex]\[ f(a) = f(-1) = (-1)^2 - (-1) - 1 = 1 + 1 - 1 = 1 \][/tex]
[tex]\[ f(b) = f(2) = 2^2 - 2 - 1 = 4 - 2 - 1 = 1 \][/tex]
[tex]\[ \text{Average rate of change} = \frac{f(2) - f(-1)}{2 - (-1)} = \frac{1 - 1}{3} = \frac{0}{3} = 0 \][/tex]
The average rate of change over interval C is [tex]\(0\)[/tex], which is exactly what we are looking for.
### Interval D: [tex]\(2 \leq x \leq 3\)[/tex]
[tex]\[ a = 2, \quad b = 3 \][/tex]
[tex]\[ f(a) = f(2) = 2^2 - 2 - 1 = 1 \][/tex]
[tex]\[ f(b) = f(3) = 3^2 - 3 - 1 = 9 - 3 - 1 = 5 \][/tex]
[tex]\[ \text{Average rate of change} = \frac{f(3) - f(2)}{3 - 2} = \frac{5 - 1}{1} = 4 \][/tex]
The average rate of change over interval D is [tex]\(4\)[/tex], which is not zero.
After analyzing all the intervals, we conclude:
The function [tex]\( f(x) = x^2 - x - 1 \)[/tex] has an average rate of change of zero over the interval:
[tex]\[ \boxed{-1 \leq x \leq 2} \][/tex]
So the correct answer is (C).
Your participation means a lot to us. Keep sharing information and solutions. This community grows thanks to the amazing contributions from members like you. For precise answers, trust IDNLearn.com. Thank you for visiting, and we look forward to helping you again soon.