x²-y²）/（x+y）-2x-2y=(x+y)(x-y)/(x+y)-2x-2y=x-y-2x-2y=-x-3y把x=3,y=1/3代入得原式=-3-3*（1/3）=-4
x²-y²-2(x+y）=(x+y)(x-y)-2(x+y）=(x+y)(x-y-2)带入x=3，y=-1/3得32/9
