Chapter 2: Problem 27
Limits of quotients Find the limits in Exercises \(23-42\) $$\lim _{t \rightarrow 1} \frac{t^{2}+t-2}{t^{2}-1}$$
Short Answer
Expert verified
The limit is \( \frac{3}{2} \).
Step by step solution
01
Identify the Limit Expression
We need to evaluate the limit of the function as \( t \) approaches 1 for the expression \( \frac{t^{2}+t-2}{t^{2}-1} \). This involves finding the behavior of the function near \( t = 1 \).
02
Attempt Direct Substitution
Substitute \( t = 1 \) directly into the function: \( \frac{1^{2}+1-2}{1^{2}-1} = \frac{0}{0} \). This results in an indeterminate form, which implies that further simplification is needed.
03
Factor the Numerator and the Denominator
Factor the numerator \( t^{2} + t - 2 \) as \((t - 1)(t + 2)\), and the denominator \( t^{2} - 1 \) as \((t - 1)(t + 1)\). The expression now becomes \( \frac{(t - 1)(t + 2)}{(t - 1)(t + 1)} \).
04
Cancel Common Factors
Since \( t eq 1 \) near the limit, we can cancel the common factor \( (t - 1) \) from the numerator and the denominator. The expression simplifies to \( \frac{t + 2}{t + 1} \).
05
Evaluate the Limit with Simplified Expression
Substitute \( t = 1 \) into the simplified function: \( \frac{1 + 2}{1 + 1} = \frac{3}{2} \). Thus, the limit is \( \frac{3}{2} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Indeterminate Forms
When solving limit problems, you may come across expressions like \( \frac{0}{0} \) or \( \frac{\infty}{\infty} \). These are known as indeterminate forms. When you first substitute the value of \( t \) into a function, if the result is an indeterminate form, it means the expression doesn't give a straightforward result.
Identifying indeterminate forms helps guide us to apply other methods for finding the limit.
- Indeterminate forms indicate that more work is needed to solve the limit.
- They occur because the limit doesn't simply equal substitution value.
Identifying indeterminate forms helps guide us to apply other methods for finding the limit.
Factoring Expressions
Factoring expressions is a key step in solving limits when you face indeterminate forms. The technique involves rewriting a polynomial as a product of its factors. In this context, factoring helps in simplifying the given expression.
For our problem:
For our problem:
- The numerator \( t^2 + t - 2 \) can be factored as \((t - 1)(t + 2)\).
- The denominator \( t^2 - 1 \) is a difference of squares, which we factor as \((t - 1)(t + 1)\).
Canceling Terms
After factoring, the expression \( \frac{(t - 1)(t + 2)}{(t - 1)(t + 1)} \) shows the common factor \( (t - 1) \) in the numerator and denominator. Cancelling this mutual term simplifies the expression, making it easier to evaluate the limit.
This newly simplified form allows direct substitution of \( t = 1 \) without encountering indeterminate forms again, making it possible to evaluate the limit as \( \frac{3}{2} \). This process emphasizes the power of simplifying through cancellation.
- Removing common factors helps eliminate the source of the indeterminate form.
- In this approach, valid only under the condition where \( t eq 1 \), since division by zero is undefined.
This newly simplified form allows direct substitution of \( t = 1 \) without encountering indeterminate forms again, making it possible to evaluate the limit as \( \frac{3}{2} \). This process emphasizes the power of simplifying through cancellation.