1,-8xy÷5x/2y2,y+2/y的平方-6y+6除（3-y）3,-8x平方y四次方乘4y六次方/3x除（-6z/x平方y）4,4-b平方/a平方-6a+9除2+b/3-a乘3a-9/a平方

当x=2,y=1 求{(x2+y2)/(x2-2xy+y2)+(2)/xy÷[(1/x)-(1/y)]}÷(x+y)的值 解方程组 ｛3x2-y2=8 {4x2+12xy+9y2=1 {x2+2xy+y2-4=0 x2+xy+y2=4 4x2-9y2=0 x2-2xy+y2-1=0还有{x2+y2=4xy-y2+4=0x2-----x的平方 y2------y的平方 还有{2x-3y=12x2-3xy+y2-4x+3y-3=0 思考题：先化简,再求值：(xy-y2)÷x2-2xy+y2/y×x2-y2/y2,其中x=1/2,y=-1 已知x2+y2-2x+4y+5=0,求(x^4-y^4)/(2x^2+xy-y^2)·[(2x-y)/(xy-y^2)]÷[(x^2+y^2)/y]^2的值 若x2-2xy-y2-x+Y-1=0 求x-y的值 若x2-2xy-y2-x+Y-1=0 求x-y的值 (x+y)(x+y+1)=0 求x2+y2+2xy的值 已知x-y+1,X2+Y2=25 求（x+y）2和x2-xy+y2的值 已知x2+4y2+x2y2-6xy+1=0,求 x4-y4/2x-y 乘 2xy-y2/xy-y2 除以（x2+y2/xy）2乘1/x+y的值 已知5x2-6xy+2y2-4x+2y+1=0,求x、y的值 (x2+y2)2与xy(x+y)2的大小 整数x,y满足x2-y2=2xy,求x-y/x+y的值 正整数x,y满足x2-y2=2xy,求x-y/x+y的值 已知y/x=1/2,求(x2+2xy+y2)/﹙x2-xy-2y2)的值. 已知x/y=3/5,求 (x2-xy+2y2)/(x2+2xy-y2)的值 已知x2+4y2+x2y2+1=6xy,则(x4-y4)/(2x2+xy-y2)*(2x-y)/(xy-y2)/(x2+y2/y)2= [2/xy/(1/x+1/y)2+(x2+y2)/(x2+2xy+y2)]*2x/(x-y) x2+2y2-2xy-2y+1=0求：x+2y的值