Question

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

Answer 1

[(x+y)(x-y)-(x-y)²-4xy]/2y

=[x²-y²-(x²-2xy+y²)-4xy]/2y

=[x²-y²-x²+2xy-y²-4xy]/2y

=[-2y²-2xy]/2y

=-y-x

=1-1

=0