Solve: $\int \frac{6x}{x^2 + 2} dx + \int \frac{4}{x(x^2 + 2)} dx$
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $2 \ln |x(x^2 + 2)| + C$
$I = \int \frac{6x}{x^2 + 2} dx + \int \frac{4}{x(x^2 + 2)} dx$
First integral: $\int \frac{6x}{x^2 + 2} dx$
Using substitution $u = x^2 + 2, du = 2x dx$, the integral simplifies to:
$3 \ln |x^2 + 2| + C_1$
Second integral: Decompose $\frac{4}{x(x^2 + 2)}$ using partial fractions:
$\frac{4}{x(x^2 + 2)} = \frac{2}{x} - \frac{2x}{x^2 + 2}$
Integrate both parts:
$\int \frac{2}{x} dx = 2 \ln |x|$
$\int \frac{2x}{x^2 + 2} dx = \ln |x^2 + 2|$
Second integral becomes: $2 \ln |x| - \ln |x^2 + 2| + C_2$
Combine the two integrals:
$3 \ln |x^2 + 2| + (2 \ln |x| - \ln |x^2 + 2|)$
$= 2 \ln |x^2 + 2| + 2 \ln |x|$
$= 2 \ln (|x(x^2 + 2)|) + C$