What is the integral of 1/(xsqrt(4x+81)) ?

The integral of 1/(xsqrt(4x+81)) is -1/9 (ln|(sqrt(4x+81))/9+1|-ln|(sqrt(4x+81))/9-1|)+C

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integral of 1/(xsqrt(4x+81))

\int \frac{1}{x 4 x + 81} d x

- \frac{1}{9} (ln \frac{4 x + 81}{9} + 1 - ln \frac{4 x + 81}{9} - 1) + C

Solution steps

\int \frac{1}{x 4 x + 81} d x

Apply u-substitution

: \int \frac{2}{u ^{2} - 81} d u

= \int \frac{2}{u ^{2} - 81} d u

Take the constant out:

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

= 2 \cdot \int \frac{1}{u ^{2} - 81} d u

Apply Integral Substitution

= 2 \cdot \int \frac{1}{9 ( v ^{2} - 1 )} d v

Take the constant out:

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

= 2 \cdot \frac{1}{9} \cdot \int \frac{1}{v ^{2} - 1} d v

Factor

v^{2} - 1 : - (- v^{2} + 1)

= 2 \cdot \frac{1}{9} \cdot \int \frac{1}{- ( - v ^{2} + 1 )} d v

Take the constant out:

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

= 2 \cdot \frac{1}{9} (- \int \frac{1}{- v ^{2} + 1} d v)

Use the common integral:

\int \frac{1}{- v ^{2} + 1} d v = \frac{ln ∣ v + 1 ∣}{2} - \frac{ln ∣ v - 1 ∣}{2}

= 2 \cdot \frac{1}{9} (- (\frac{ln ∣ v + 1 ∣}{2} - \frac{ln ∣ v - 1 ∣}{2}))

Substitute back

= 2 \cdot \frac{1}{9} - \frac{ln \frac{4 x + 81}{9} + 1}{2} - \frac{ln \frac{4 x + 81}{9} - 1}{2}

Simplify

2 \cdot \frac{1}{9} - \frac{ln \frac{4 x + 81}{9} + 1}{2} - \frac{ln \frac{4 x + 81}{9} - 1}{2} : - \frac{1}{9} (ln \frac{4 x + 81}{9} + 1 - ln \frac{4 x + 81}{9} - 1)

= - \frac{1}{9} (ln \frac{4 x + 81}{9} + 1 - ln \frac{4 x + 81}{9} - 1)

Add a constant to the solution

= - \frac{1}{9} (ln \frac{4 x + 81}{9} + 1 - ln \frac{4 x + 81}{9} - 1) + C

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What is the integral of 1/(xsqrt(4x+81)) ?
The integral of 1/(xsqrt(4x+81)) is -1/9 (ln|(sqrt(4x+81))/9+1|-ln|(sqrt(4x+81))/9-1|)+C