Chapter 5: Problem 1
Let \(f(x)=x^{2} .\) Find a value \(c \in(-1,2)\) so that \(f^{\prime}(c)\) equals the slope between the endpoints of \(f(x)\) on [-1,2]
Short Answer
Expert verified
The value of \( c \) is \( \frac{1}{2} \).
Step by step solution
01
Find the slope between the endpoints
First, identify the endpoints of the function on the interval [-1, 2]. Calculate the slope using the formula for the slope of a line, which is \( m = \frac{f(b) - f(a)}{b - a} \), where \( f(x) = x^2 \), \( a = -1 \), and \( b = 2 \). This gives:\[f(-1) = (-1)^2 = 1, \quad f(2) = 2^2 = 4\]Thus, the slope \( m \) is:\[m = \frac{4 - 1}{2 + 1} = \frac{3}{3} = 1\]
02
Compute the derivative of the function
Find the derivative of the function \( f(x) = x^2 \). Use the power rule, which states that the derivative of \( x^n \) is \( nx^{n-1} \). For \( x^2 \), the derivative is:\[f'(x) = 2x\]
03
Set derivative equal to slope and solve for c
Now, equate the derivative \( f'(x) = 2x \) to the slope found in Step 1, which is 1:\[2c = 1\]Solve for \( c \):\[c = \frac{1}{2}\]
04
Verify that c is within the given interval
Ensure that the value of \( c \) we found is within the interval (-1, 2). Since \( c = \frac{1}{2} \), verify:\[-1 < \frac{1}{2} < 2\]Thus, \( c \) is indeed within the given interval.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope of a Line
Understanding the slope of a line is a fundamental concept in mathematics, particularly in calculus and algebra. It represents the rate at which one variable changes in relation to another. For a straight line, the slope is constant and can be quickly calculated using two points on the line.
- The slope is determined by the formula \( m = \frac{y_2 - y_1}{x_2 - x_1} \), where \((x_1, y_1)\) and \((x_2, y_2)\) are two distinct points on the line.
- This formula gives the vertical change (rise) per unit of horizontal change (run).
- In our exercise, the points are derived from the function values at the endpoints of the interval, which were \((-1,1)\) and \((2,4)\) on the curve \(f(x) = x^2\).
Derivative
In calculus, the derivative is a measure of how a function changes as its input changes. Think of it as a tool that tells you the slope of the tangent line to the function at any point, providing a snapshot of the function's behavior.
- For a function \( f(x) \), the derivative \( f'(x) \) quantifies the instantaneous rate of change of \( f \) with respect to \( x \).
- The process of finding a derivative is called differentiation.
- Derivatives can vary across the domain of a function. For instance, \( f(x) = x^2 \) has a derivative \( f'(x) = 2x \), meaning the slope of the function's tangent line changes linearly with \( x \).
Power Rule
The power rule is a quick and efficient technique for finding the derivative of a function that involves a variable raised to a power. It is one of the building blocks of calculus, simplifying many differentiation tasks.
- The power rule states that for any real number \( n \), the derivative of \( x^n \) is \( nx^{n-1} \).
- This rule is particularly useful as it eliminates the need for using the limit-based definition of a derivative for each term.
- In the given exercise, the power rule was applied to derive \( f'(x) = 2x \) from \( f(x) = x^2 \), demonstrating how easy and efficient it is to analyze the rate of change for polynomials.