What is the integral of (3x^3+x)/((x^2+1)^2) ?

The integral of (3x^3+x)/((x^2+1)^2) is 3/2 ln|x^2+1|+1/(x^2+1)+C

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integral of (3x^3+x)/((x^2+1)^2)

\int \frac{3 x ^{3} + x}{( x ^{2} + 1 ) ^{2}} d x

\frac{3}{2} ln x^{2} + 1 + \frac{1}{x ^{2} + 1} + C

Solution steps

\int \frac{3 x ^{3} + x}{( x ^{2} + 1 ) ^{2}} d x

Expand

\frac{3 x ^{3} + x}{( x ^{2} + 1 ) ^{2}} : \frac{3 x ^{3}}{( x ^{2} + 1 ) ^{2}} + \frac{x}{( x ^{2} + 1 ) ^{2}}

Apply the Sum Rule:

\int f (x) \pm g (x) d x = \int f (x) d x \pm \int g (x) d x

= \int \frac{3 x ^{3}}{( x ^{2} + 1 ) ^{2}} d x + \int \frac{x}{( x ^{2} + 1 ) ^{2}} d x

\int \frac{3 x ^{3}}{( x ^{2} + 1 ) ^{2}} d x = \frac{3}{2} (ln x^{2} + 1 + \frac{1}{x ^{2} + 1})

\int \frac{x}{( x ^{2} + 1 ) ^{2}} d x = - \frac{1}{2 ( x ^{2} + 1 )}

= \frac{3}{2} (ln x^{2} + 1 + \frac{1}{x ^{2} + 1}) - \frac{1}{2 ( x ^{2} + 1 )}

Simplify

\frac{3}{2} (ln x^{2} + 1 + \frac{1}{x ^{2} + 1}) - \frac{1}{2 ( x ^{2} + 1 )} : \frac{3}{2} ln x^{2} + 1 + \frac{1}{x ^{2} + 1}

= \frac{3}{2} ln x^{2} + 1 + \frac{1}{x ^{2} + 1}

Add a constant to the solution

= \frac{3}{2} ln x^{2} + 1 + \frac{1}{x ^{2} + 1} + C

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What is the integral of (3x^3+x)/((x^2+1)^2) ?
The integral of (3x^3+x)/((x^2+1)^2) is 3/2 ln|x^2+1|+1/(x^2+1)+C