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Give the partial fraction decomposition for the following expressions. \(\frac{2 x^{2}+5 x+6}{x^{2}+3 x+2}\) (Hint: Use long division first.)

Short Answer

Expert verified
Question: Find the partial fraction decomposition of the given expression: \(\frac{2 x^{2}+5 x+6}{x^{2}+3 x+2}\) Answer: The partial fraction decomposition of the given expression is \(\frac{2 x^{2}+5 x+6}{x^{2}+3 x+2} = 2 + \frac{1}{x+1} - \frac{2}{x+2}\).

Step by step solution

01

Long Division

Perform long division to divide the numerator \(2x^2 + 5x + 6\) by the denominator \(x^2 + 3x + 2\): ``` ____________________________ x^2 + 3x + 2 | 2x^2 + 5x + 6 - (2x^2 + 6x + 4) ____________________________ -1x + 2 ``` The quotient obtained is 2, and the remainder is \(-x + 2\).
02

Rewrite the Expression Using Quotient and Remainder

Now, rewrite the given expression using the quotient and remainder: \(\frac{2 x^{2}+5 x+6}{x^{2}+3 x+2} = 2 + \frac{-x + 2}{x^2 + 3x +2}\)
03

Partial Fraction Decomposition

Finally, perform the partial fraction decomposition on the fraction part: \(\frac{-x + 2}{x^2 + 3x + 2} = \frac{A}{x+1} + \frac{B}{x+2}\) Combine the right-hand side fractions: \(-x + 2 = A(x+2) + B(x+1)\) Expanding and equating the polynomial coefficients: \(-x + 2 = (A+B)x + 2A + B\) Comparing the coefficients, we get the following system of equations: \(A+B=-1\) (coefficient of \(x\)) \(2A+B=2\) (constant term) Solving this system of equations, we get \(A=1\) and \(B=-2\). Finally, the partial fraction decomposition of the given expression is: \(\frac{2 x^{2}+5 x+6}{x^{2}+3 x+2} = 2 + \frac{1}{x+1} - \frac{2}{x+2}\)

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Key Concepts

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

Long Division
Let's delve into the concept of long division, a foundational technique used to divide numbers or polynomial expressions. This method involves writing down the dividend and divisor in a structured format, similar to setting up a fraction. The objective is to determine how many times the divisor fits into the dividend.

Here's how it works in our exercise: You divide the leading term of the numerator (\(2x^2\)) by the leading term of the denominator (\(x^2\)), obtaining 2. The next step is to multiply the entire divisor by 2 and subtract the result from the original numerator. This subtraction gives us the 'remainder'. In our case, the remainder is \( -x + 2 \). If there was no remainder, the division would be complete; however, with a remainder, we must continue to the next step.
Polynomial Long Division
Polynomial long division is a technique applied when dividing polynomials, which extends from the long division method used for numbers.

As seen in the solution to the exercise, after establishing the quotient and remainder, you rewrite the original polynomial as the sum of this quotient and a fraction whose numerator is the remainder and denominator is the original divisor. This repackaging neatly sets us up for partial fraction decomposition.

Polynomial long division is a critical preliminary step when the degree of the numerator is greater than or equal to the degree of the denominator. It simplifies the expression and aids in further integration or solving of algebraic equations.
Integrals
The concept of integrals is central in calculus and refers to finding the area under a curve. When a function is given in the form of a complex fraction, like the one in our exercise, it's often beneficial to perform partial fraction decomposition before integration.

The reason is, simpler fractions stemming from this process are easier to integrate. Our example resulted in a constant plus two separate fractions. Integrating a constant is straightforward, and there are well-established integration rules for the types of fractions (\(\frac{1}{x+1}\) and \(\frac{1}{x+2}\)) that we've acquired through decomposition.
Algebraic Equations
Algebraic equations express relationships between variables and constants. They can be simple linear expressions or complex, multifaceted polynomial ones.

In partial fraction decomposition, as seen in the solution, we encounter a system of algebraic equations when determining the constants A and B. We derive these equations by equating coefficients of like terms of polynomials on both sides. Then, by solving this system, typically through substitution or elimination methods, we find the values for A and B, which are crucial parts in getting to the final decomposed form of the initial polynomial fraction.

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Most popular questions from this chapter

Let \(R\) be the region between the curves \(y=e^{-c x}\) and \(y=-e^{-c x}\) on the interval \([a, \infty),\) where \(a \geq 0\) and \(c>0 .\) The center of mass of \(R\) is located at \((\bar{x}, 0)\) where \(\bar{x}=\frac{\int_{a}^{\infty} x e^{-c x} d x}{\int_{a}^{\infty} e^{-c x} d x} .\) (The profile of the Eiffel Tower is modeled by the two exponential curves; see the Guided Project The exponential Eiffel Tower. ) a. For \(a=0\) and \(c=2,\) sketch the curves that define \(R\) and find the center of mass of \(R .\) Indicate the location of the center of mass. b. With \(a=0\) and \(c=2,\) find equations of the lines tangent to the curves at the points corresponding to \(x=0\) c. Show that the tangent lines intersect at the center of mass. d. Show that this same property holds for any \(a \geq 0\) and any \(c>0 ;\) that is, the tangent lines to the curves \(y=\pm e^{-c x}\) at \(x=a\) intersect at the center of mass of \(R\)

Trapezoid Rule and Simpson's Rule Consider the following integrals and the given values of \(n .\) a. Find the Trapezoid Rule approximations to the integral using \(n\) and \(2 n\) subintervals. b. Find the Simpson's Rule approximation to the integral using \(2 n\) subintervals. It is easiest to obtain Simpson's Rule approximations from the Trapezoid Rule approximations, as in Example \(8 .\) c. Compute the absolute errors in the Trapezoid Rule and Simpson's Rule with \(2 n\) subintervals. $$\int_{0}^{1} e^{2 x} d x, n=25$$

Evaluate the following improper integrals (Putnam Exam, 1939 ). a. \(\int_{1}^{3} \frac{d x}{\sqrt{(x-1)(3-x)}} \quad\) b. \(\int_{1}^{\infty} \frac{d x}{e^{x+1}+e^{3-x}}\)

Three cars, \(A, B,\) and \(C,\) start from rest and accelerate along a line according to the following velocity functions: $$v_{A}(t)=\frac{88 t}{t+1}, \quad v_{B}(t)=\frac{88 t^{2}}{(t+1)^{2}}, \quad \text { and } \quad v_{C}(t)=\frac{88 t^{2}}{t^{2}+1}$$ a. Which car travels farthest on the interval \(0 \leq t \leq 1 ?\) b. Which car travels farthest on the interval \(0 \leq t \leq 5 ?\) c. Find the position functions for each car assuming each car starts at the origin. d. Which car ultimately gains the lead and remains in front?

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