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Popular Calculus >

integral of x/(x-21)

Solution

\int \frac{x}{x - 21} d x

Solution

x - 21 + 21 ln ∣ x - 21 ∣ + C

Solution steps

\int \frac{x}{x - 21} d x

Apply u-substitution

= \int \frac{u + 21}{u} d u

Expand

\frac{u + 21}{u} : 1 + \frac{21}{u}

= \int 1 + \frac{21}{u} d u

Apply the Sum Rule:

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

= \int 1 d u + \int \frac{21}{u} d u

\int 1 d u = u

\int \frac{21}{u} d u = 21 ln ∣ u ∣

= u + 21 ln ∣ u ∣

Substitute back

u = x - 21

= x - 21 + 21 ln ∣ x - 21 ∣

Add a constant to the solution

= x - 21 + 21 ln ∣ x - 21 ∣ + C

Graph

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Frequently Asked Questions (FAQ)

What is the integral of x/(x-21) ?
The integral of x/(x-21) is x-21+21ln|x-21|+C