（x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2),其中x=1-根号2 y=根号2-2

（x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2),其中x=1-根号2 y=根号2-2 x根号x+x根号y/xy-y^2)-（x+根号xy+y/x根号x-y根号）y {（x-y)/(根号x+根号y)}-(x+y-2倍根号xy)/(根号x-根号y)=? (x+y)/(根号下x+根号下y)+2xy/(x根号下y+y根号下x)=______. 已知y=根号(x-8)+根号(8-x)+18,求代数式[(x+y)/(根号x+根号y)]-2xy/(x根号y-y根号x) 【(x-y)^3(x^1/2+y^1/2)^-3+3(x根号y-y根号x)】/(x根号x+y根号y)+(2xy根号xy- 已知y=根号1-x+根号x-1+3,求根号x+根号y分之x+2根号xy+y+根号x-根号y分之一的值 化简:((根号x-根号y)^3+2x根号x+y根号y)/(x根号x+y根号y)+(3根号xy-3y)/(x-y) 先化简再求值(x+y)(x-y)-(4x的立方y-8xy的立方)/2xy,其中x=-1,y=3/根号3 先化简再求值（x-y/1-x+y/1）÷x平方+2xy+y平方/2y,其中x=根号3+2,y=根号3 先化简再求值：xy^3÷(-xy)+(x+2y)(x-2y),其中x=根号2,y=1 已知实数x.y满足根号(x+y-8)+根号(8-x-y)=根号(3x-y-4)+根号(x-2y+7),求x,y