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For the following exercises, find the decomposition of the partial fraction for the nonrepeating linear factors. $$\frac{-x-24}{x^{2}-2 x-24}$$

Short Answer

Expert verified
\(\frac{-3}{x-6} + \frac{2}{x+4}\)

Step by step solution

01

Factor the Denominator

The given expression is \(\frac{-x-24}{x^2-2x-24}\). First, factor the quadratic denominator. We are looking for two numbers that multiply to \(-24\) and add up to \(-2\). These numbers are \(-6\) and \(+4\). Thus, the factored form of the denominator is \((x - 6)(x + 4)\).
02

Set Up the Partial Fraction Decomposition

With the denominator factored as \((x-6)(x+4)\), we express the fraction as a sum of two simpler fractions: \(\frac{-x-24}{(x-6)(x+4)} = \frac{A}{x-6} + \frac{B}{x+4}\). This is our partial fraction decomposition setup.
03

Clear the Denominator

Multiply both sides of the equation by \((x-6)(x+4)\) to clear the denominator: \[-x-24 = A(x+4) + B(x-6).\] This eliminates the fraction, allowing us to solve for the constants \(A\) and \(B\).
04

Solve for Constants A and B

Expand and simplify the equation: \[-x - 24 = Ax + 4A + Bx - 6B.\]Combine like terms: \[-x - 24 = (A + B)x + (4A - 6B).\]This gives us a system of equations by comparing coefficients:1. \(A + B = -1\)2. \(4A - 6B = -24\).
05

Solve the System of Equations

Solve the system of equations:1. \(A + B = -1\)2. \(4A - 6B = -24\)First, solve equation 1 for \(A\):\[A = -1 - B\]Substitute this into equation 2:\[4(-1-B) - 6B = -24\]\[-4 - 4B - 6B = -24\]\[-4 - 10B = -24\]Add 4 to both sides:\[-10B = -20\]Divide by \(-10\):\[B = 2\]Substitute back to find \(A\):\[A = -1 - 2\]\[A = -3\]
06

Write the Decomposition

Substitute \(A = -3\) and \(B = 2\) back into the partial fraction decomposition: \[\frac{-x-24}{(x-6)(x+4)} = \frac{-3}{x-6} + \frac{2}{x+4}.\]This is the partial fraction decomposition of the given expression.

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Key Concepts

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

Nonrepeating Linear Factors
In partial fraction decomposition, nonrepeating linear factors are distinct first-degree polynomials that don't repeat in the denominator's factorization. For example, in the expression \( \frac{-x-24}{(x-6)(x+4)} \), both \( x-6 \) and \( x+4 \) are nonrepeating linear factors. This means they appear only once in the factorization of the polynomial in the denominator.

Identifying these factors is crucial as each one will correspond to a separate fraction in the partial fraction decomposition. When you split the expression into parts, there will be one distinct fraction for each nonrepeating factor, each with its own constant in the numerator.
  • The expression can be represented as \( \frac{A}{x-6} + \frac{B}{x+4} \), where \( A \) and \( B \) are the constants to be determined.
Nonrepeating linear factors simplify the solving process since they lead to simpler systems of equations, compared to higher degree or repeating factors.
Factoring Quadratics
Factoring quadratics is the process of breaking down a quadratic expression into simpler products of linear expressions. For example, the expression \( x^2-2x-24 \) needs to be factored to find its roots or zero points.

The goal in factoring a quadratic like \( x^2-2x-24 \) is to find two numbers that multiply to the constant term, \(-24\), and add up to the linear coefficient, \(-2\). In this case, the numbers \(-6\) and \(+4\) fit these criteria. Therefore, the quadratic \( x^2 - 2x - 24 \) factors into \((x - 6)(x + 4)\).
  • Factoring Steps:
  • Look for two numbers that multiply to the product of the leading coefficient and the constant term.
  • Ensure these numbers also add to the linear coefficient.
  • Rewrite the quadratic as a product of two binomials using these numbers.
Factoring quadratics is fundamental in partial fraction decomposition, as it helps in breaking down the rational expression into simpler fractions.
System of Equations
A system of equations is formed when trying to determine the coefficients in a partial fraction decomposition. In our example, this occurs after eliminating the denominators and equating coefficients from both sides of the equation.

For the expression \( -x - 24 = A(x+4) + B(x-6) \), expanding and combining like terms gives \( (A + B)x + (4A - 6B) = -x - 24 \). From here, a system of equations is obtained by comparing coefficients:
  • \( A + B = -1 \)
  • \( 4A - 6B = -24 \)
Solving this system provides the values of \( A \) and \( B \), which are the numerators in the partial fractions.

Systems of equations can be solved using various methods such as substitution or elimination. Here, substitution makes it easy to find \( A \) after determining \( B \). Understanding how to solve such systems is crucial for completing partial fraction decomposition.
Rational Expressions
Rational expressions are fractions where the numerator and the denominator are polynomials. They can appear complex, but partial fraction decomposition can break them into simpler, more manageable pieces.

Taking the example \( \frac{-x-24}{x^2-2x-24} \), the numerator \(-x-24\) is a first-degree polynomial, and the denominator \(x^2-2x-24\) is a quadratic polynomial. The goal is to express this rational expression as a sum of simpler fractions.
  • These simpler fractions are easier to integrate or differentiate if needed in calculus.
  • They provide insights into behavior of functions, such as finding vertical asymptotes.
Working with rational expressions involves understanding how to manipulate and transform them, typically through factoring and decomposition, to make them useful for solving more complex problems.

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Most popular questions from this chapter

For the following exercises, set up the augmented matrix that describes the situation, and solve for the desired solution. You invested \(\$ 10,000\) into two accounts: one that has simple \(3 \%\) interest, the other with \(2.5 \%\) interest. If your total interest payment after one year was \(\$ 283.50\), how much was in each account after the year passed?

For the following exercises, create a system of linear equations to describe the behavior. Then, solve the system for all solutions using Cramer’s Rule. You invest \(\$ 10,000\) into two accounts, which receive 8\(\%\) interest and 5\(\%\) interest. At the end of a year, you had \(\$ 10,710\) in your combined accounts. How much was invested in each account?

For the following exercises, set up the augmented matrix that describes the situation, and solve for the desired solution. A major appliance store is considering purchasing vacuums from a small manufacturer. The store would be able to purchase the vacuums for \(\$ 86\) each, with a delivery fee of \(\$ 9,200\), regardless of how many vacuums are sold. If the store needs to start seeing a profit after 230 units are sold, how much should they charge for the vacuums?

For the following exercises, set up the augmented matrix that describes the situation, and solve for the desired solution. A bag of mixed nuts contains cashews, pistachios, and almonds. There are \(1,000\) total nuts in the bag, and there are 100 less almonds than pistachios. The cashews weigh 3 \(\mathrm{g}\) , pistachios weigh 4 \(\mathrm{g}\) , and almonds weigh 5 \(\mathrm{g}\) . If the bag weighs \(3.7 \mathrm{kg},\) find out how many of each type of nut is in the bag.

For the following exercises, create a system of linear equations to describe the behavior. Then, solve the system for all solutions using Cramer’s Rule. Your garden produced two types of tomatoes, one green and one red. The red weigh 10 oz, and the green weigh 4 oz. You have 30 tomatoes, and a total weight of 13 lb, 14 oz. How many of each type of tomato do you have?

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