Question

x²-y²/x²+2xy+y² 减 x+y/x-y ,其中x=1 ,y=-3 【

Answer 1

x²-y²/x²+2xy+y² － x+y/x-y

=(x+y)(x-y)/(x+y)²-(x+y)/(x-y)

=(x-y)/(x+y)-(x+y)/(x-y)

=[(x-y)²-(x+y)²]/[(x+y)(x-y)]

=-4xy/(x²-y²)

=-4×1×(-3)/(1-9)

=3/2