# Math Help - Strange problem with chain rule

1. ## Strange problem with chain rule

derive x&#47;&#40;1-x&#94;2&#41; - Wolfram|Alpha

How on earth does 1-x^2 become x^2-1?!

Thanks.

2. ## Re: Strange problem with chain rule

$(1-x^2)^2 = x^4 - 2x^2 + 1$
$(x^2-1)^2 = x^4 - 2x^2 + 1$

This is because, for square functions f(-x) = f(x)

3. ## Re: Strange problem with chain rule

Originally Posted by jakncoke
$(1-x^2)^2 = x^4 - 2x^2 + 1$
$(x^2-1)^2 = x^4 - 2x^2 + 1$
Doh..I did suspect that, but I dismissed it as being too far out. Why go through the step of re-arranging it. Weird calculator.