Chapter 2: Problem 10
Exercises \(5-10\) refer to the function $$f(x)=\left\\{\begin{array}{ccc}{x^{2}-1,} & {-1 \leq x < 0} \\ {2 x,} & {0 < x < 1} \\ {1,} & {x=1} \\ {-2 x+4,} & {1 < x < 2} \\ {0,} & {2 < x<3}\end{array}\right.$$ graphed in the accompanying figure. To what new value should \(f(1)\) be changed to remove the discontinuity?
Short Answer
Step by step solution
Identify the Discontinuity at x = 1
Evaluate the Limit from the Left
Evaluate the Limit from the Right
Compare Limits and Function Value at x = 1
Determine the New Value for f(1)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Piecewise Functions Explained
Understanding piecewise functions involves:
- Defining segments: Each part of the function \(f(x)\) is defined for a specific range of \(x\). For example, for the given function \(f(x)\), \(x\) values are divided into multiple ranges with corresponding expressions like \(x^2 - 1\), \2x\, \1\, etc.
- Checking endpoints: Attention must be given to where each segment starts and ends, and whether it is inclusive or exclusive. In our case, notice carefully how some parts use \(-1 \leq x < 0\) while others like \(1 < x < 2\) rely on exclusivity.
- Smooth transitions: The goal is often to have transitions at the endpoints be as seamless as possible, eliminating any sudden jumps which create discontinuities.
Understanding Limits
Here’s how limits work:
- Left-hand limit: This represents the value that \(f(x)\) approaches as \(x\) comes close to a particular point from the left (denoted as \(x \to c^-\)). For the problem, \(\lim_{{x \to 1^-}} 2x=2\).
- Right-hand limit: Conversely, this is the value that \(f(x)\) approaches as \(x\) approaches from the right (denoted as \(x \to c^+\)). Example: \(\lim_{{x \to 1^+}} (-2x + 4) = 2\).
- Overall limit: For a limit at a point to exist, both the left-hand limit and right-hand limit should be the same. If they are equal, that common value is the limit of the function at \(x = c\).
Dealing with Discontinuous Functions
To address discontinuities:
- Identifying the break: Breaks are located where the piecewise function rules change, or the function changes abruptly at a point. In our exercise, this was identified at \(x = 1\).
- Matching limits: As seen in the problem, making adjustments to ensure the left-hand and right-hand limits are equal can sometimes be enough. E.g., both limits at \(x = 1\) needed to equal 2 to remove the discontinuity.
- Adjusting the function value: Often, we fix discontinuities by modifying the value the function takes at that specific point. For the exercise, \(f(1)\) was adjusted from 1 to 2 to achieve continuity.