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Evaluate the following integrals. $$\int \frac{6}{x^{2}-1} d x$$

Short Answer

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Question: Evaluate the integral of the following rational function: $$\int \frac{6}{x^{2}-1} dx$$ Answer: $$\int \frac{6}{x^{2}-1} dx = 3\ln|x-1| - 3\ln|x+1| + C$$

Step by step solution

01

Identify the Integrals as Rational Functions

Observe that the integrand is a rational function, which is a fraction with a polynomial in the numerator and denominator. Since the degree of the polynomial in the denominator is greater than the degree of the polynomial in the numerator, we don't need to perform long division.
02

Perform Partial Fraction Decomposition

Now we need to decompose the rational function into simpler parts by using partial fraction decomposition. The denominator can be factored as \((x-1)(x+1)\). In the partial fraction decomposition, we will have: $$\frac{6}{x^2 - 1} = \frac{A}{(x-1)} + \frac{B}{(x+1)}$$ Multiplying both sides by \(x^2 - 1\), we get: $$6 = A(x+1) + B(x-1)$$
03

Solve for Constants A and B

To find the values of A and B, plug in two values for x that will eliminate one of the variables. For example, let us choose \(x = 1\) and \(x = -1\): For \(x = 1\): $$6 = A(1+1)$$ $$A = 3$$ For \(x = -1\): $$6 = B(-1-1)$$ $$B = -3$$ So we have: $$\frac{6}{x^2-1} = \frac{3}{x-1} - \frac{3}{x+1}$$
04

Integrate Term by Term

Now that the rational function is decomposed, we can integrate term by term. We have: $$\int \frac{6}{x^{2}-1} d x=\int\left(\frac{3}{x-1} - \frac{3}{x+1}\right) d x$$ The integrals can now be directly calculated as: $$\int \frac{6}{x^{2}-1} d x=3\int\frac{1}{x-1} d x -3\int\frac{1}{x+1} d x$$
05

Solve the Integrals

Apply the reverse chain rule. We have: $$\int \frac{6}{x^{2}-1} d x=3\ln|x-1| -3\ln|x+1| + C$$ Where \(C\) is the constant of integration.
06

Final Answer

The integral of the given function is: $$\int \frac{6}{x^{2}-1} d x = 3\ln|x-1| - 3\ln|x+1| + C$$

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