1. ## finding differential

Find the differential of each function.
y = (1+r^4)^-2

I used the power + chain rule and got

$-8r^3/(1+r^4)^3$

what am i doing wrong?

2. Originally Posted by break
Find the differential of each function.
y = (1+r^4)^-2

I used the power + chain rule and got

$-8r^3/(1+r^4)^3$

what am i doing wrong?
Nothing, except forgetting the notation.

With diffferentials

$dy=f'(x)dx$

So, tag on a $dx$ 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.

3. ohh yeah it was the "dr" i was forgetting. i feel so dumb thanks haha.

4. Originally Posted by break
ohh yeah it was the "dr" i was forgetting. i feel so dumb thanks haha.
Hmmm...

Are you sure, because now I'm wondeering whether or not $r\text{ varies with t}$, perhaps?

Are you doing a related rates problem or something?