What is the integral of 1/(x^2-2x-4) ?

The integral of 1/(x^2-2x-4) is -1/(2sqrt(5))(ln|(x-1)/(sqrt(5))+1|-ln|(x-1)/(sqrt(5))-1|)+C

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integral of 1/(x^2-2x-4)

\int \frac{1}{x ^{2} - 2 x - 4} d x

- \frac{1}{2 5} (ln \frac{x - 1}{5} + 1 - ln \frac{x - 1}{5} - 1) + C

Solution steps

\int \frac{1}{x ^{2} - 2 x - 4} d x

Factor

x^{2} - 2 x - 4 : - (- x^{2} + 2 x + 4)

= \int \frac{1}{- ( - x ^{2} + 2 x + 4 )} d x

Take the constant out:

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

= - \int \frac{1}{- x ^{2} + 2 x + 4} d x

Complete the square

- x^{2} + 2 x + 4 : - (x - 1)^{2} + 5

= - \int \frac{1}{- ( x - 1 ) ^{2} + 5} d x

Apply u-substitution

: \int \frac{1}{- u ^{2} + 5} d u

= - \int \frac{1}{- u ^{2} + 5} d u

Apply Integral Substitution

= - \int \frac{1}{5 ( - v ^{2} + 1 )} d v

Take the constant out:

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

= - \frac{1}{5} \cdot \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}

= - \frac{1}{5} (\frac{ln ∣ v + 1 ∣}{2} - \frac{ln ∣ v - 1 ∣}{2})

Substitute back

= - \frac{1}{5} \frac{ln \frac{x - 1}{5} + 1}{2} - \frac{ln \frac{x - 1}{5} - 1}{2}

Simplify

- \frac{1}{5} \frac{ln \frac{x - 1}{5} + 1}{2} - \frac{ln \frac{x - 1}{5} - 1}{2} : - \frac{1}{2 5} (ln \frac{x - 1}{5} + 1 - ln \frac{x - 1}{5} - 1)

= - \frac{1}{2 5} (ln \frac{x - 1}{5} + 1 - ln \frac{x - 1}{5} - 1)

Add a constant to the solution

= - \frac{1}{2 5} (ln \frac{x - 1}{5} + 1 - ln \frac{x - 1}{5} - 1) + C

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What is the integral of 1/(x^2-2x-4) ?
The integral of 1/(x^2-2x-4) is -1/(2sqrt(5))(ln|(x-1)/(sqrt(5))+1|-ln|(x-1)/(sqrt(5))-1|)+C