/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 28 Algebraically determine the limi... [FREE SOLUTION] | 91Ó°ÊÓ

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Algebraically determine the limits. $$ \lim _{t \rightarrow-3} \frac{t^{2}-4 t-21}{t+3} $$

Short Answer

Expert verified
The limit is \(-10\).

Step by step solution

01

Identify the Type of Limit

The given limit can be expressed as \( \lim _{t \rightarrow -3} \frac{t^{2}-4t-21}{t+3} \). Notice that both the numerator \(t^2 - 4t - 21\) and the denominator \(t + 3\) are polynomials. When the denominator evaluates to zero at \(t = -3\), we're dealing with a potential indeterminate form if the numerator is also zero at this point.
02

Check for Indeterminate Form

Substitute \(t = -3\) into both the numerator and the denominator. For the numerator: \((-3)^2 - 4(-3) - 21 = 9 + 12 - 21 = 0\). For the denominator: \(-3 + 3 = 0\). Thus, substituting directly into the expression results in \(\frac{0}{0}\), confirming an indeterminate form.
03

Factor the Numerator

To resolve the indeterminate form, factor the numerator \(t^2 - 4t - 21\). Look for two numbers that multiply to \(-21\) and add to \(-4\). These numbers are \(-7\) and \(3\). Thus, we can factor the numerator as \((t - 7)(t + 3)\).
04

Simplify the Expression

Substitute the factored numerator back into the original limit expression: \( \lim _{t \rightarrow -3} \frac{(t - 7)(t + 3)}{t + 3} \). Then, simplify by canceling the common factor \((t + 3)\) from the numerator and denominator. The expression simplifies to \( \lim _{t \rightarrow -3} (t - 7) \).
05

Evaluate the Limit

With the simplified expression, directly substitute \(t = -3\) into \(t - 7\): \(-3 - 7 = -10\). Thus, the limit is \(-10\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Algebraic simplification
In calculus, algebraic simplification is a powerful tool to make complex expressions more manageable and easier to evaluate. When dealing with limits, especially those that initially appear as indeterminate forms like \( \frac{0}{0} \), simplification techniques can reveal the true behavior of the expression.For our problem, we began with the expression \( \lim _{t \rightarrow -3} \frac{t^{2}-4t-21}{t+3} \). By substituting directly, we faced an indeterminate form. To overcome this, recognizing that simplifying the expression can often reveal removable discontinuities or hidden behaviors is crucial.Utilizing algebraic skills, we factored the polynomial in the numerator to reveal common factors with the denominator. By canceling these common factors, we simplified the expression and were able to evaluate the limit directly. This process not only resolves the indeterminate form but also makes the expression easier to interpret.
Indeterminate forms
When calculating limits, it's common to encounter indeterminate forms. These are expressions where simple substitution fails, leading to results like \( \frac{0}{0} \) or \( \frac{\infty}{\infty} \). These forms don't have a defined outcome, so special measures like simplification are needed.In our example, substituting \( t = -3 \) into \( \frac{t^{2}-4t-21}{t+3} \) resulted in the indeterminate form \( \frac{0}{0} \). This tells us that while the substitution gives zero in both the numerator and the denominator, it doesn't tell us the behavior of the expression near \( t = -3 \).To resolve this, we use algebraic simplification or other methods like L'Hôpital's Rule in different contexts. These tools help us to remove or bypass the undefined behavior and find the true limit of the function. Ignoring indeterminate forms might lead to misunderstanding a function's behavior, so addressing them is vital.
Polynomial factoring
Polynomial factoring is an essential technique in both algebra and calculus, used to break down complex polynomial expressions into simpler, multiplied factors. This method is particularly useful in resolving indeterminate forms when evaluating limits.In our exercise, the quadratic polynomial in the numerator, \( t^{2} - 4t - 21 \), was factored into \((t - 7)(t + 3)\). Factoring involves finding two numbers that multiply to give the constant term \(-21\) and sum to give the linear coefficient \(-4\). These numbers were \(-7\) and \(3\).By factoring, we uncovered a common factor \((t + 3)\) shared by both the numerator and the denominator. This allowed us to cancel it out, simplifying the expression and removing the indeterminate form. Factoring can thus transform complicated polynomial-based limits into straightforward expressions that are easier to evaluate.

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Most popular questions from this chapter

Input and output notation is given for two functions. Determine whether the pair of functions can be combined by function composition. If so, then a. draw an input/output diagram for the new function. b. write a statement for the new function complete with function notation and input and output units and descriptions. The revenue from the sale of \(x\) soccer uniforms is \(R(x)\) yen. The dollar value of \(r\) yen is \(D(r)\) dollars.

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