The problem asks us to evaluate the indefinite integral $\int \frac{x+5}{x^2+x-2} \, dx$. The problem also provides a partial fraction decomposition, so we just need to evaluate the integral of the decomposed expression: $\int (\frac{2}{x-1} - \frac{1}{x+2}) \, dx$.

AnalysisCalculusIntegrationIndefinite IntegralPartial FractionsLogarithms
2025/5/20

1. Problem Description

The problem asks us to evaluate the indefinite integral x+5x2+x2dx\int \frac{x+5}{x^2+x-2} \, dx. The problem also provides a partial fraction decomposition, so we just need to evaluate the integral of the decomposed expression: (2x11x+2)dx\int (\frac{2}{x-1} - \frac{1}{x+2}) \, dx.

2. Solution Steps

First, we observe that x2+x2=(x1)(x+2)x^2+x-2 = (x-1)(x+2). Thus, we can write
x+5x2+x2=x+5(x1)(x+2). \frac{x+5}{x^2+x-2} = \frac{x+5}{(x-1)(x+2)}.
The given partial fraction decomposition is
x+5x2+x2=2x11x+2. \frac{x+5}{x^2+x-2} = \frac{2}{x-1} - \frac{1}{x+2}.
Now we integrate both sides with respect to xx:
x+5x2+x2dx=(2x11x+2)dx. \int \frac{x+5}{x^2+x-2} \, dx = \int \left(\frac{2}{x-1} - \frac{1}{x+2}\right) \, dx.
We can split the integral:
(2x11x+2)dx=2x1dx1x+2dx. \int \left(\frac{2}{x-1} - \frac{1}{x+2}\right) \, dx = \int \frac{2}{x-1} \, dx - \int \frac{1}{x+2} \, dx.
Now we can take out the constant 2 from the first integral:
21x1dx1x+2dx. 2 \int \frac{1}{x-1} \, dx - \int \frac{1}{x+2} \, dx.
We know that 1udu=lnu+C\int \frac{1}{u} \, du = \ln |u| + C. Let u=x1u = x-1, then du=dxdu = dx. Let v=x+2v = x+2, then dv=dxdv = dx. Thus,
\int \frac{1}{x-1} \, dx = \int \frac{1}{u} \, du = \ln |u| + C_1 = \ln |x-1| + C_

1. $$

\int \frac{1}{x+2} \, dx = \int \frac{1}{v} \, dv = \ln |v| + C_2 = \ln |x+2| + C_

2. $$

Substituting these results back into the original expression, we get
2lnx1lnx+2+C, 2 \ln |x-1| - \ln |x+2| + C,
where CC is the constant of integration. Using logarithm properties, we can write
lnx12lnx+2+C=ln(x1)2x+2+C. \ln |x-1|^2 - \ln |x+2| + C = \ln \left|\frac{(x-1)^2}{x+2}\right| + C.

3. Final Answer

ln(x1)2x+2+C\ln \left|\frac{(x-1)^2}{x+2}\right| + C

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