Hello there,

Doing a bit of integration using substitution and when i come to sub back in i have come across an interesting case:

Lets say that:

$\displaystyle u^2 = x+1$

then what would $\displaystyle u^3$ be?

I have come up with:

$\displaystyle (x+1)\sqrt{x+1}$

Is that correct?

What i have is:

$\displaystyle u^3(\frac{2}{5}u^2 - \frac{2}{3})$

is there an easy way to take the fraction out?

...okay well ive got it like this:

$\displaystyle \frac{1}{15}u^3(6u^2-10)$

is that right?