Chapter 2: Problem 39
In the following exercises, set up a table of values to find the indicated limit. Round to eight digits. $$ \lim _{x \rightarrow 1}(1-2 x) $$
Short Answer
Expert verified
The limit is -1.
Step by step solution
01
Identify the Function
We need to find the limit of the function \( f(x) = 1 - 2x \) as \( x \) approaches 1. The target value is \( x = 1 \).
02
Choose Values Close to 1
To approximate the limit, we choose values of \( x \) that are close to 1 both from the left (e.g., 0.9, 0.99, 0.999) and from the right (e.g., 1.1, 1.01, 1.001).
03
Calculate the Function Values
Compute the value of \( 1-2x \) for each chosen \( x \): - For \( x = 0.9 \), \( f(x) = 1 - 2(0.9) = 1 - 1.8 = -0.8 \) - For \( x = 0.99 \), \( f(x) = 1 - 2(0.99) = 1 - 1.98 = -0.98 \) - For \( x = 0.999 \), \( f(x) = 1 - 2(0.999) = 1 - 1.998 = -0.998 \) - For \( x = 1.1 \), \( f(x) = 1 - 2(1.1) = 1 - 2.2 = -1.2 \) - For \( x = 1.01 \), \( f(x) = 1 - 2(1.01) = 1 - 2.02 = -1.02 \) - For \( x = 1.001 \), \( f(x) = 1 - 2(1.001) = 1 - 2.002 = -1.002 \)
04
Analyze the Table of Values
Create a table with the \( x \) and corresponding \( f(x) \) values:\[\begin{array}{|c|c|}\hlinex & f(x) \\hline0.9 & -0.8 \0.99 & -0.98 \0.999 & -0.998 \1.001 & -1.002 \1.01 & -1.02 \1.1 & -1.2 \\hline\end{array}\] Notice that as \( x \) approaches 1, \( f(x) \) tends toward -1.
05
Conclude the Limit
Based on the table of values, as \( x \) approaches 1, the value of \( f(x) \) approaches -1. Thus, \(\lim _{x \rightarrow 1}(1 - 2x) = -1.\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Evaluation
In calculus, function evaluation is the process of determining the output of a function for a specified input. For the exercise given, you are dealing with the function \( f(x) = 1 - 2x \). Evaluating this function means calculating \( f(x) \) for different values of \( x \). This involves substituting the value of \( x \) into the equation, performing the arithmetic operation. For example, when \( x = 0.9 \), substituting gives \( f(0.9) = 1 - 2(0.9) = -0.8 \). Function evaluation helps to understand how changes in \( x \) affect \( f(x) \). It's the foundation of limit finding, as you explore the behavior of \( f(x) \) near a specific point.
Approaching Values
In limits, 'approaching values' refers to the process of getting closer and closer to a particular point on the \( x \)-axis but never actually reaching it. For the limit \( \lim _{x \rightarrow 1}(1 - 2x) \), you are interested in seeing how \( f(x) \) behaves as \( x \) gets very close to 1, without necessarily being exactly 1. Imagine standing at a crossroads and taking tiny steps towards a particular junction, observing changes as you move. As you approach 1 from either direction (either incrementally decreasing from the right or increasing from the left), you analyze how \( f(x) \) behaves to determine its limiting value.
Table of Values
A table of values is a simple yet effective tool to visualize how a function behaves as \( x \) approaches a target value. In this exercise, a table is used to show various \( x \) values closely surrounding 1, both from the left (e.g., 0.9, 0.99, 0.999) and from the right (e.g., 1.1, 1.01, 1.001). For each \( x \), you compute \( f(x) \) and note the results:
- 0.9 gives -0.8
- 0.99 gives -0.98
- 0.999 gives -0.998
- 1.1 gives -1.2
- 1.01 gives -1.02
- 1.001 gives -1.002
Limit Calculation Steps
To calculate the limit, follow specific steps to ensure accuracy and completeness.
- Identify the Function: Recognize the function you're evaluating, such as \( f(x) = 1 - 2x \), for which you find the limit as \( x \) approaches a certain value.
- Choose Values Around the Target: Select values incrementally nearer to the target value of \( x = 1 \) from both sides (left and right).
- Evaluate the Function: Determine \( f(x) \) for each chosen \( x \). This helps understand the approaching behavior of the function.
- Analyze the Results: Look at the trends in \( f(x) \) as \( x \) gets close to the target. Here, you observed \( f(x) \) nears -1 as \( x \) approaches 1.
- Conclude: Based on observations, formalize the limit statement, such as \( \lim _{x \rightarrow 1}(1 - 2x) = -1 \).