Chapter 4: Problem 71
Graph the functions in Exercises \(71-74 .\) Then find the extreme values of the function on the interval and say where they occur. $$ f(x)=|x-2|+|x+3|, \quad-5 \leq x \leq 5 $$
Short Answer
Expert verified
Min value is 2 at \(x=-3\); max value is 11 at \(x=5\).
Step by step solution
01
Understanding the Function
The function given is composed of two absolute value expressions: \( f(x) = |x-2| + |x+3| \). This results in a piecewise function where different expressions apply based on the value of \( x \), specifically depending on when the expressions inside the absolute value change sign.
02
Identifying Critical Points
The critical points for the absolute value expressions \(|x-2|\) and \(|x+3|\) occur at \(x = 2\) and \(x = -3\) respectively. These points define where the expressions change their behavior, creating pieces in the piecewise function.
03
Analyzing Each Piece
1. For \(x < -3\), both terms are negative, so \(f(x) = -(x-2) - (x+3) = -2x - 1\).2. For \(-3 \leq x < 2\), the term \(x+3\) becomes positive and \(x-2\) remains negative, so \(f(x) = -(x-2) + (x+3) = x + 5\).3. For \(x \geq 2\), both terms become positive, so \(f(x) = (x-2) + (x+3) = 2x + 1\).
04
Evaluate at Interval and Critical Points
Calculate the function values at the endpoints and critical points: - At \(x = -5\), \(f(-5) = -2(-5) - 1 = 9\).- At \(x = -3\), \(f(-3) = (-3) + 5 = 2\).- At \(x = 2\), \(f(2) = 2(2) + 1 = 5\).- At \(x = 5\), \(f(5) = 2(5) + 1 = 11\).
05
Identify Extreme Values
Compare the values calculated:- The minimum value is \(2\), occurring at \(x = -3\).- The maximum value is \(11\), occurring at \(x = 5\). The extreme values are determined by considering both the endpoints and critical points of the given interval.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Functions
Graphing functions is a fundamental skill in mathematics that involves plotting a set of points on a coordinate plane to represent a function. When we graph a function like \( f(x) = |x-2| + |x+3| \), it helps us visualize how the function behaves over its domain.
To graph a function accurately, follow these steps:
To graph a function accurately, follow these steps:
- Identify key points such as intercepts, turning points, and critical points.
- Determine the behavior of the function as \( x \) approaches infinity or negative infinity.
- Evaluate the function at several points within its domain to gain insight into its shape.
Piecewise Function
A piecewise function consists of multiple sub-functions, each applying to a certain interval of the domain. The given function \( f(x) = |x-2| + |x+3| \) is an excellent example of a piecewise function because it is defined by different expressions depending on the intervals of \( x \).
The breakdown is as follows:
The breakdown is as follows:
- For \( x < -3 \), the expression is \( -2x - 1 \).
- For \( -3 \leq x < 2 \), the expression is \( x + 5 \).
- For \( x \geq 2 \), the expression is \( 2x + 1 \).
Critical Points
Critical points are vital in understanding a function's graphical behavior because they represent where the derivative is zero or undefined, often indicating local maxima or minima.
In the context of \( f(x) = |x-2| + |x+3| \), the critical points occur at \( x = -3 \) and \( x = 2 \). These points are where the expressions \(|x-2|\) and \(|x+3|\) change signs, affecting the shape and slope of the graph.
To determine critical points:
In the context of \( f(x) = |x-2| + |x+3| \), the critical points occur at \( x = -3 \) and \( x = 2 \). These points are where the expressions \(|x-2|\) and \(|x+3|\) change signs, affecting the shape and slope of the graph.
To determine critical points:
- Delineate the intervals defined by the points of change.
- Examine the sign changes of the derivative within these intervals.
- Evaluate how these points affect the continuity and differentiability of the function.
Absolute Value Function
An absolute value function refers to a function that involves expressions enclosed within absolute value symbols, optimizing the output for non-negative values.
The expression \(|x-2|\) changes to \(x-2\) if \(x\geq 2\), and \(2-x\) if \(x<2\). Similarly, \(|x+3|\) changes to \(x+3\) if \(x\geq -3\) and \(-x-3\) if \(x<-3\).
It's essential to grasp the behavior of absolute value functions as they often involve sudden changes in slope and direction, leading to distinctive V-shaped graphs. Recognizing how:
The expression \(|x-2|\) changes to \(x-2\) if \(x\geq 2\), and \(2-x\) if \(x<2\). Similarly, \(|x+3|\) changes to \(x+3\) if \(x\geq -3\) and \(-x-3\) if \(x<-3\).
It's essential to grasp the behavior of absolute value functions as they often involve sudden changes in slope and direction, leading to distinctive V-shaped graphs. Recognizing how:
- The function handles different sign changes.
- Impact its symmetry and periodic behavior.
- Influence on optimization problems when evaluating distances or differences between two points.