Chapter 3: Problem 67
Find the average rate of change of \(g(x)=x^{3}-4 x+7\) : (a) From -3 to -2 (b) From -1 to 1 (c) From 1 to 3
Short Answer
Expert verified
a) 15, b) -3, c) 9
Step by step solution
01
Identify the formula for the average rate of change
The average rate of change of a function between two points is given by: \[\text{Average Rate of Change} = \frac{g(b) - g(a)}{b - a}\]where \(g(x)\) is the function, and \(a\) and \(b\) are the two points.
02
Calculate the average rate of change from -3 to -2
First, find \(g(-3)\) and \(g(-2)\).\[g(-3) = (-3)^3 - 4(-3) + 7 = -27 + 12 + 7 = -8\]\[g(-2) = (-2)^3 - 4(-2) + 7 = -8 + 8 + 7 = 7\]Now apply the formula:\[\frac{g(-2) - g(-3)}{-2 - (-3)} = \frac{7 - (-8)}{-2 + 3} = \frac{15}{1} = 15\]
03
Calculate the average rate of change from -1 to 1
First, find \(g(-1)\) and \(g(1)\).\[g(-1) = (-1)^3 - 4(-1) + 7 = -1 + 4 + 7 = 10\]\[g(1) = (1)^3 - 4(1) + 7 = 1 - 4 + 7 = 4\]Now apply the formula:\[\frac{g(1) - g(-1)}{1 - (-1)} = \frac{4 - 10}{1 + 1} = \frac{-6}{2} = -3\]
04
Calculate the average rate of change from 1 to 3
First, find \(g(1)\) and \(g(3)\).\[g(1) = (1)^3 - 4(1) + 7 = 1 - 4 + 7 = 4\]\[g(3) = (3)^3 - 4(3) + 7 = 27 - 12 + 7 = 22\]Now apply the formula:\[\frac{g(3) - g(1)}{3 - 1} = \frac{22 - 4}{3 - 1} = \frac{18}{2} = 9\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Difference Quotient
The difference quotient is a critical concept in calculus that simplifies finding the average rate of change for a function. In essence, it measures the change in the function's value over a specified interval. The formula is: \[ \text{Difference Quotient} = \frac{g(b) - g(a)}{b - a} \] where \( g(x) \) represents the function, and \( a \) and \( b \) denote the two points in the interval. Simply put, it calculates how much the function's output values change when moving from \( a \) to \( b \). Remember, understanding the difference quotient is essential for delving deeper into calculus topics like derivatives.
Polynomial Functions
A polynomial function consists of coefficients and variables raised to non-negative integer powers. They take the form: \[ g(x) = a_n x^n + a_{n-1} x^{n-1} + \ldots + a_1 x + a_0 \] In our exercise, the function given is a third-degree polynomial: \[ g(x) = x^3 - 4x + 7 \]. Here are some key points to remember:
- The degree is the highest power of the variable (3 in this case).
- Polynomials are continuous and smooth functions.
- They are straightforward to evaluate for given values of x.
Function Evaluation
Function evaluation is a method of finding the function's output for specific input values. In our exercise, we evaluated the function \( g(x) \) at different points. For example, \[ g(-3) = (-3)^3 - 4(-3) + 7 = -27 + 12 + 7 = -8 \] Evaluating a function involves substituting the variable with the given number and simplifying the expression. Here are the steps to remember:
- Substitute the input value in place of the variable.
- Perform arithmetic operations, following the order of operations (PEMDAS/BODMAS).
- Arrive at the final output or value.
Step-by-Step Solutions
Breaking down problems into smaller, manageable steps ensures better understanding and reduces errors. In this exercise, each part was solved incrementally:
- Step 1: Identify the formula for the average rate of change.
- Step 2: Evaluate the function values at the given points.
- Step 3: Apply the average rate of change formula.
- First, find \( g(-3) \) and \( g(-2) \): \[ g(-3) = -8 \] \[ g(-2) = 7 \]
- Second, apply the formula: \[ \frac{g(-2) - g(-3)}{-2 - (-3)} = \frac{15}{1} = 15 \]