1、[x(x-3)]/(x²+2)=0＝》x(x-3)=0＝》x=0或x=3
2x/(x²-1)+2x/(1-x)=2x/(x²-1)-2x(x+1)/(x²-1)=2x²/(1-x²)
当x=0,2x/(x²-1)+2x/(1-x)=0
当x=3,2x/(x²-1)+2x/(1-x)=-9/4
2、[(2x+y )/(x²-2xy+y²)] × (x-y)=[(2x+y )/(x-y)²]× (x-y)=)=(2x+y )/(x-y)
因为x-3y=0＝》x=3y
所以[(2x+y )/(x²-2xy+y²)] × (x-y)=(2x+y )/(x-y)=(6y+y )/(3y-y)=7/2