Question

Rearranging terms in using difference of perfect squares (1-x^2) vs (x^2-1)

Answer 1

>Distribute the negative  
>  
>\- (x + 1)(x – 1) = (-x + 1)(-x – 1)

You put the negative in both groups.  There is only one negative, so you'd only negate either (x+1) or (x-1), not both.

Answer 2

-(x^2 +1) = -x^2 -1. This is not difference of two squares.

a^2 -b^2 = -(b^2 -a^2 )