Calculus!!!!?

Question

Find d³y/dx³

y= (x+1)²/x-1

I'm so lost with this problem! I don't know if I did it right if someone else could try it and see if its the same or see what I did wrong that would be great!!! Thanx.

Linz

Answer 1

The answer I got is 2.

But I'm not sure about it. I forget the rules. Can you get dy/dx by doing the numerator and the denominator separately? If so, then I'm pretty sure the answer is 2.

I got that by multiplying (x+1)(x+1) to get xsquared +2x + 1
the first deriviative of that is 2X+2 the first derivative of the denominator is 1
so, to get the second deriviative, all you have to do is find dy/dx of 2X + 2 ....which is 2

oh....is it the third derivative you need... well....if my proceedure is correct then the answer is 0....

I have no idea where the 4s came from in that other answer...

Answer 2

y= (x+1)²/(x-1)

y
= [(x-1)^2+4x-4+4]/(x-1)
= (x-1) + 4 + 4/(x-1)

y'''
=8/(x-1)^3
------------
cato,
(x+1)^2
=x^2+2x+1
=x^2-2x+4x+1
=x^2-2x+1+4x-4+4
=(x-1)^2+4(x-1)+4