Chapter 7: Problem 25
Evaluate the integral. $$\int \frac{2 x^{2}-10 x+4}{(x+1)(x-3)^{2}} d x$$
Short Answer
Expert verified
The integral evaluates to \(2 \ln|x+1| - \frac{4}{x-3} + C\).
Step by step solution
01
Decompose into Partial Fractions
First, decompose the integrand \( \frac{2x^2 - 10x + 4}{(x+1)(x-3)^2} \) into partial fractions. We assume a form:\[\frac{2x^2 - 10x + 4}{(x+1)(x-3)^2} = \frac{A}{x+1} + \frac{B}{x-3} + \frac{C}{(x-3)^2}\]Multiply through by the denominator \((x+1)(x-3)^2\) to eliminate the denominators.
02
Set Up the Equation
Expand the equation:\[2x^2 - 10x + 4 = A(x-3)^2 + B(x+1)(x-3) + C(x+1)\]Now, simplify and equate coefficients for powers of \(x\) to solve for \(A\), \(B\), and \(C\).
03
Solve for Coefficients
1. Equate coefficients for \(x^2\), \(x\), and the constant term.2. Solve the system of equations to find \(A = 2\), \(B = 0\), \(C = -4\).The partial fraction decomposition is:\[\frac{2}{x+1} + \frac{0}{x-3} + \frac{-4}{(x-3)^2} = \frac{2}{x+1} - \frac{4}{(x-3)^2}\]
04
Integrate the Individual Terms
Now integrate each term separately:1. \( \int \frac{2}{x+1} \, dx = 2 \ln|x+1| + C_1 \)2. \( \int \frac{-4}{(x-3)^2} \, dx = 4 \cdot \frac{1}{x-3} + C_2 \)Combine these results.
05
Write the Final Answer
The integral evaluates to:\[2 \ln|x+1| - \frac{4}{x-3} + C\]where \(C\) is a constant of integration.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Partial Fraction Decomposition
Partial fraction decomposition is a technique used to break down complex rational expressions into simpler fractions that are easier to integrate or differentiate. Consider the expression in our original exercise:
- We have \(\frac{2x^2 - 10x + 4}{(x+1)(x-3)^2}\).
- The first step in partial fraction decomposition is to express it as a sum of simpler fractions.
- Eliminate the denominators by multiplying through by the common denominator \( (x+1)(x-3)^2 \).
- This results in an equation we can expand and simplify.
- By matching coefficients of corresponding \(x\) powers, we establish equations to solve for \(A\), \(B\), and \(C\).
Definite Integrals
Definite integrals calculate the exact area under a curve between two specific values along the x-axis, known as bounds. In the context of definite integrals:
- We assess an integral from a lower limit \(a\) to an upper limit \(b\).
- The notation for definite integrals is \( \int_a^b f(x) \, dx \).
- This integral yields a number representing the net area under the curve \(f(x)\) from \(x = a\) to \(x = b\).
Indefinite Integrals
Indefinite integrals represent a family of functions and incorporate an arbitrary constant since they do not have sold bounds like definite integrals. In solving our exercise, we evaluated indefinite integrals:
- The indefinite integral of a function \(f(x)\) is written as \( \int f(x) \, dx \).
- This integral results in a function \(F(x) + C\), where \(F(x)\) is the antiderivative of \(f(x)\) and \(C\) is the constant of integration.
- We found that \( \int \frac{2}{x+1} \, dx = 2 \ln|x+1| + C_1 \).
- Similarly, \( \int \frac{-4}{(x-3)^2} \, dx = 4 \cdot \frac{1}{x-3} + C_2 \).