Question

先化简。再求值 x分子x减y除与括号x减x分之2xy减y的平方 其中x等于2 y等于负1

急急急 求全过程 感谢啊
急急急 大神们快写啊

Answer 1

x分之(x-y) ÷ [x- x分之(2xy-y²)]
=x分之(x-y)÷[x分之(x²-2xy+y²)]
=x分之(x-y)* [(x-y)²分之x]
=(x-y)分之1
=（2+1）分之1
=3分之1

Answer 2

(x-y)/x÷[x-(2xy-y²)/x]
解：原式=(x-y)/x÷[(x²-2xy+y²)/x]
=(x-y)/x×x/(x-y)²
=1/(x-y)
当x=2，y=-1时代入得：
原式=1/[2-(-1)]=1/3