Show that the average rate of change of the linear function f(x) = a over any interval say [x1,x2] is the constant a. %3D

Calculus: Early Transcendentals
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Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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**Problem Statement:**

3. Show that the average rate of change of the linear function \( f(x) = ax + b \) over any interval, say \([x_1, x_2]\), is the constant \( a \).

**Solution Explanation:**

To find the average rate of change of the function \( f(x) = ax + b \) over an interval \([x_1, x_2]\), we use the formula for the average rate of change:

\[
\text{Average rate of change} = \frac{f(x_2) - f(x_1)}{x_2 - x_1}
\]

1. Calculate \( f(x_2) \) and \( f(x_1) \):

\[
f(x_2) = a \cdot x_2 + b
\]

\[
f(x_1) = a \cdot x_1 + b
\]

2. Substitute these into the average rate of change formula:

\[
\frac{(a \cdot x_2 + b) - (a \cdot x_1 + b)}{x_2 - x_1}
\]

3. Simplify the expression:

\[
= \frac{a \cdot x_2 + b - a \cdot x_1 - b}{x_2 - x_1}

= \frac{a \cdot (x_2 - x_1)}{x_2 - x_1}
\]

4. Cancel \( (x_2 - x_1) \) from the numerator and the denominator:

\[
= a
\]

Thus, the average rate of change of the linear function \( f(x) = ax + b \) over the interval \([x_1, x_2]\) is indeed the constant \( a \).
Transcribed Image Text:**Problem Statement:** 3. Show that the average rate of change of the linear function \( f(x) = ax + b \) over any interval, say \([x_1, x_2]\), is the constant \( a \). **Solution Explanation:** To find the average rate of change of the function \( f(x) = ax + b \) over an interval \([x_1, x_2]\), we use the formula for the average rate of change: \[ \text{Average rate of change} = \frac{f(x_2) - f(x_1)}{x_2 - x_1} \] 1. Calculate \( f(x_2) \) and \( f(x_1) \): \[ f(x_2) = a \cdot x_2 + b \] \[ f(x_1) = a \cdot x_1 + b \] 2. Substitute these into the average rate of change formula: \[ \frac{(a \cdot x_2 + b) - (a \cdot x_1 + b)}{x_2 - x_1} \] 3. Simplify the expression: \[ = \frac{a \cdot x_2 + b - a \cdot x_1 - b}{x_2 - x_1} = \frac{a \cdot (x_2 - x_1)}{x_2 - x_1} \] 4. Cancel \( (x_2 - x_1) \) from the numerator and the denominator: \[ = a \] Thus, the average rate of change of the linear function \( f(x) = ax + b \) over the interval \([x_1, x_2]\) is indeed the constant \( a \).
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