# Thread: Integrating (x² + 1)² using substitution

1. ## Integrating (x² + 1)² using substitution

Hey forum how would I go about in order to compute this indefinite integral,

$\displaystyle \int \, (x^2 +1)^2 \, \text{d}x \ ?$

I can't seem to eliminate all $\displaystyle x$-variables using $\displaystyle u = x^2 + 1$. I know I can simply compute it by expanding the integrand but I want to do it using substitution in particular.

3. ## Re: Integrating (x² + 1)² using substitution

Originally Posted by SweatingBear
Hey forum how would I go about in order to compute this indefinite integral,

$\displaystyle \int \, (x^2 +1)^2 \, \text{d}x \ ?$

I can't seem to eliminate all $\displaystyle x$-variables using $\displaystyle u = x^2 + 1$. I know I can simply compute it by expanding the integrand but I want to do it using substitution in particular.
You can't do this using substitution. Expand the integrand instead.

4. ## Re: Integrating (x² + 1)² using substitution

Originally Posted by Prove It
You can't do this using substitution.
How come?