Chapter 13: Problem 46
Use a table and/or graph to decide whether each limit exists. If a limit exists, find its value. \(\lim _{x \rightarrow 1} f(x),\) where \(f(x)=\left\\{\begin{array}{ll}3 x-5 & \text { if } x \leq 1 \\ 6-2 x & \text { if } x>1\end{array}\right.\)
Short Answer
Expert verified
The limit does not exist.
Step by step solution
01
Understanding the problem
The function \( f(x) \) is piecewise, with \( f(x) = 3x - 5 \) when \( x \leq 1 \) and \( f(x) = 6 - 2x \) when \( x > 1 \). We need to determine if the limit of \( f(x) \) as \( x \) approaches 1 exists, and if it does, find its value.
02
Analyzing from the left of 1
Evaluate \( f(x) \) as \( x \) approaches 1 from the left (\( x \to 1^- \)). Since \( f(x) = 3x - 5 \) when \( x \leq 1 \), substitute \( x = 1 \) to find \( f(1) = 3(1) - 5 = -2 \). This is the value of the function as you approach from the left.
03
Analyzing from the right of 1
Evaluate \( f(x) \) as \( x \) approaches 1 from the right (\( x \to 1^+ \)). Here, \( f(x) = 6 - 2x \) since \( x > 1 \). Substitute \( x = 1 \) to get \( 6 - 2(1) = 4 \). This is the value of the function as \( x \) approaches 1 from the right.
04
Compare the left and right limits
For the limit to exist, the left-hand limit and right-hand limit must be equal. We found the left limit to be \(-2\) and the right limit to be \(4\). Since \(-2 eq 4\), the limits do not match.
05
Conclusion
Since the left-hand limit and the right-hand limit are not equal, the limit \( \lim _{x \rightarrow 1} f(x) \) does not exist.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Piecewise Functions
Piecewise functions are mathematical expressions defined by multiple sub-functions, each of which applies to a specific interval of the input domain. This allows us to describe a function that behaves differently in different parts of its input range. For instance, in the function given in the problem,
- When the input, or \( x \), is less than or equal to 1, the function is defined as \( 3x - 5 \).
- When \( x \) is greater than 1, the function changes to \( 6 - 2x \).
Left-Hand Limit
The left-hand limit is the value that a function approaches as the input approaches a specified point from the left side (i.e., from values less than the point of interest). In the given problem, we are interested in the behavior as \( x \) approaches 1 from values less than 1, denoted as \( x \to 1^- \).
For the piecewise function provided, when \( x \leq 1 \), the function is defined as \( 3x - 5 \). Therefore, to find the left-hand limit, we substitute \( x = 1 \) into the expression \( 3x - 5 \). This gives us:
For the piecewise function provided, when \( x \leq 1 \), the function is defined as \( 3x - 5 \). Therefore, to find the left-hand limit, we substitute \( x = 1 \) into the expression \( 3x - 5 \). This gives us:
- \( 3(1) - 5 = -2 \)
Right-Hand Limit
The right-hand limit considers the value that a function approaches as the input comes from values greater than a specified point. For this exercise, we need to evaluate the limit as \( x \to 1^+ \).
In the piecewise function, the relevant segment for \( x > 1 \) is \( 6 - 2x \). To compute the right-hand limit, we substitute \( x = 1 \) into the expression \( 6 - 2x \). This results in:
In the piecewise function, the relevant segment for \( x > 1 \) is \( 6 - 2x \). To compute the right-hand limit, we substitute \( x = 1 \) into the expression \( 6 - 2x \). This results in:
- \( 6 - 2(1) = 4 \)
Discontinuity Analysis
Discontinuity analysis involves examining whether a function has any jumps or breaks at a particular point. A key aspect of this analysis is comparing left-hand and right-hand limits to determine if they are the same.
In the exercise at hand, we found:
In the exercise at hand, we found:
- The left-hand limit as \( x \to 1^- \) is \(-2\).
- The right-hand limit as \( x \to 1^+ \) is \( 4 \).