Looking for someone good at math! (Calculus)

[samisdumm]

(x^2+1)^4/(x^2-1)^4 is the same thing as ((x^2+1)/(x^2-1))^4 right?

When i take the derivative of the first one and the second one, I came up with different answers, help!

 

[Koggit]

yeah, it's the same thing.. how are you taking the derivative? IMO the easy way is to just expand each quantity first, you don't have to deal with the chain rule, just some algebra that your calculator can handle.

Let's say..

f1 = (x^2+1)^4 = 1 + 4 x^2 + 6 x^4 + 4 x^6 + x^8
therefore f1' = 8 x + 24 x^3 + 24 x^5 + 8 x^7
f2 = (x^2-1)^4 = 1 - 4 x^2 + 6 x^4 - 4 x^6 + x^8
therefore f2' = -8 x + 24 x^3 - 24 x^5 + 8 x^7

then you want the derivative of f1/f2. You use the quotient rule..

[(f1')(f2) - (f1)(f2')] / (f2)^2


edit: I went ahead and differentiated it in mathematica so you have something to check your answer against