Chapter 2: Problem 12
Estimating a limit from tables Let \(f(x)=\frac{x^{3}-1}{x-1}\) a. Calculate \(f(x)\) for each value of \(x\) in the following table. b. Make a conjecture about the value of \(\lim _{x \rightarrow 1} \frac{x^{3}-1}{x-1}\)
Short Answer
Expert verified
Answer: The conjectured limit is 3.
Step by step solution
01
Calculate f(x) for each value of x in the table
To calculate \(f(x)\) for the values of \(x\) in the table, we will simply plug in the value of \(x\) into the function for each entry and simplify:
\(f(x)=\frac{x^3-1}{x-1}\)
The table values are not provided, so we will create a small table with some example values for \(x\):
| x | f(x) |
|---|------|
| 0.9| |
| 0.99| |
| 1.01| |
| 1.1 | |
Calculating the values of \(f(x)\) for each value of \(x\):
\(-\frac{(0.9)^3-1}{0.9-1}=0.9^2+0.9+1\approx2.71\)
\(-\frac{(0.99)^3-1}{0.99-1}=0.99^2+0.99+1\approx2.9701\)
\(\frac{(1.01)^3-1}{1.01-1}=1.01^2+1.01+1\approx3.0301\)
\(\frac{(1.1)^3-1}{1.1-1}=1.1^2+1.1+1\approx3.31\)
Now, our table is:
| x | f(x) |
|---|------|
| 0.9| 2.71 |
| 0.99| 2.9701|
| 1.01| 3.0301|
| 1.1 | 3.31 |
02
Make a conjecture about the limit of f(x) as x approaches 1
The table shows that the value of \(f(x)\) gets closer to \(3\) as \(x\) approaches \(1\). We can observe this from the table entries:
When \(x\) is slightly less than 1 (\(0.9\) and \(0.99\)), \(f(x)\) is also slightly less than 3 (\(2.71\) and \(2.9701\)).
When \(x\) is slightly greater than 1 (\(1.01\) and \(1.1\)), \(f(x)\) is also slightly greater than 3 (\(3.0301\) and \(3.31\)).
Given this pattern, it seems likely that the limit of \(f(x)\) as \(x\) approaches 1 is 3.
Therefore, our conjecture is:
\(\lim_{x \rightarrow 1} \frac{x^3-1}{x-1} = 3\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Estimating Limits
In calculus, understanding how to estimate the limit of a function as the variable approaches a particular value is crucial. This involves observing the behavior of the function for values close to the point of interest. For our exercise, we deal with the function \(f(x)=\frac{x^3-1}{x-1}\). By evaluating this function at different values of \(x\) near 1, we can estimate the limit of \(f(x)\) as \(x\) approaches 1.Here's how you do it:
- Choose values that are very close to 1, both smaller and larger, such as 0.9, 0.99, 1.01, and 1.1.
- Calculate \(f(x)\) for each of these values.
- Observe how these results behave as \(x\) gets very close to 1.
Function Evaluation
Function evaluation is the process of calculating the output of a function given certain values of the variable. In this exercise, we evaluated \(f(x) = \frac{x^3-1}{x-1}\) for values of \(x\) near 1.As you substitute each value into \(f(x)\), you perform the arithmetic operations to simplify the expression. This can sometimes include a bit of algebra, especially when working with polynomial fractions like this one. Let's break it down:
- Substitute \(x\) with the given number. For example, for \(x=0.9\), you substitute it into the function \(\frac{(0.9)^3-1}{0.9-1}\).
- Simplify the expression by performing the calculations, ensuring to maintain accuracy with decimals.
- Repeat for other values such as 0.99, 1.01, and 1.1.
Conjecture Formulation
Formulating a conjecture involves making a reasoned guess based on observed data. In our case, after evaluating \(f(x)\) for values approaching 1, you notice the outputs gravitating towards a consistent number.The steps in arriving at a conjecture are:
- Observe the calculated values of \(f(x)\) and identify a trend. In this problem, values like 2.71, 2.9701, 3.0301, and 3.31 suggest an approach towards 3.
- Understand the tendency of the function, whether it increases, decreases, or levels off around the point of interest.
- Based on these observations, posit that \(\lim_{x \to 1} \frac{x^3-1}{x-1} = 3\).