先化简再求值(x²+xy-2y²)/(x²-2xy+y²)

先化简再求值(x²+xy-2y²)/(x²-2xy+y²)
先化简再求值(x²+xy-2y²)/(x²-2xy+y²)

先化简再求值(x²+xy-2y²)/(x²-2xy+y²)
原式=（x-y）（x+2y）除以（x-y）（x-y）-(1-x方y的四次方)-x方y的四次方
=(x+2y)除以（x-y）-1
当x=根3+根2,y=根3-根2
上式=（3倍根3-根2）除以（2倍根2）-1