Hey

So im doing integrals of fractions for my monday testm but theres somehting i dont get about the formula

$\displaystyle integrate(dx/(a^2-u^2)$

I have

However the book says

Why is this?? It took u=(3x+1) and a=sqrt(2) but it inverted them on the logarithm part??

So it ended up using $\displaystyle integrate dx/(u^2-a^2)$ instead..

Thanks for the help ;D