What is the integral of x/(4+9x^2) ?

The integral of x/(4+9x^2) is 1/18 ln|4+9x^2|+C

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integral of x/(4+9x^2)

\int \frac{x}{4 + 9 x ^{2}} d x

\frac{1}{18} ln 4 + 9 x^{2} + C

Solution steps

\int \frac{x}{4 + 9 x ^{2}} d x

Apply u-substitution

: \int \frac{1}{18 u} d u

= \int \frac{1}{18 u} d u

Take the constant out:

\int a \cdot f (x) d x = a \cdot \int f (x) d x

= \frac{1}{18} \cdot \int \frac{1}{u} d u

Use the common integral:

\int \frac{1}{u} d u = ln (∣ u ∣)

= \frac{1}{18} ln ∣ u ∣

Substitute back

u = 4 + 9 x^{2}

= \frac{1}{18} ln 4 + 9 x^{2}

Add a constant to the solution

= \frac{1}{18} ln 4 + 9 x^{2} + C

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x \to - 2 lim (2)

f (x) = e^{5 x} cos (8 x)

What is the integral of x/(4+9x^2) ?
The integral of x/(4+9x^2) is 1/18 ln|4+9x^2|+C