Find the differential of each function.
y = (1+r^4)^-2
I used the power + chain rule and got
$\displaystyle -8r^3/(1+r^4)^3$
what am i doing wrong?
Nothing, except forgetting the notation.
With diffferentials
$\displaystyle dy=f'(x)dx$
So, tag on a $\displaystyle dx$ and you're all set.
Unless, of course, by 'differential', you actually meant to say 'derivative'. If this is thecase, maybe you're looking at the wrong answer manual.