Question

=[y^2*x+x-y-x^2*y]/[(x^2+1)(y^2+1)] =[(x-y)+xy(y-x)}/[(x^2+1

Answer 1

[y^2*x+x-y-x^2*y]/[(x^2+1)(y^2+1)] =[(x-y)+xy(y-x)}/[(x^2+1)(y^2+1)] ,对的.

因为y^2*x+x-y-x^2*y=xy*(y-x)+(x-y)=(x-y)(xy+1),

而不是(x-y)(x^2+y^2+1).