若x/y=2/7,求x^2-3xy+2y^2/2x^2-3xy+7y^2的值.

若1/x-1/y=2,求3x-2xy-3y/x-xy-y的值3x-2xy-3y/x-xy-y 不好意思，是3x-2xy-3y/x-2xy-y 若(y-x)/xy=3,求分式(2x+3xy-2y)/(x-2xy-y)的值 若y-x/xy=3,求分式2x+3xy-2y/x-2xy-y 若x+y-5xy=0,求(2x-3xy+2y)/(x+2xy+y)的值 若xy=2（x+y),求 （3x-5xy+3y)÷(-x+3xy-y) 的值 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 已知x=3y,试求（x-y)^2+2xy-y^2/x^2+7xy+y^2 已知x=3y,试求(x-y)^2+2xy-y^2/x^2+7xy+y^2 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 若x^2+xy+y=14,y^2+xy+x=28,求x+y 已知xy^2=-2求xy（2x^3y^7+5x^2y 若x+y=4,x^3+y^3=(x+y)(x^2-xy+y^2)z,求x^3+12xy+y^3的值. 若根号x+y-3+绝对值xy+x+y-2=0,求x/y+y/x根号x+y-3+绝对值xy+x+y-2=0,求x/y+y/x 若x+y=4,x-y=6,求xy(y^2+y)-y^2(xy+2x)-3xy的值. 已知X/Y=2/7,求x^2-3XY+2Y^2/X^2-2XY+Y^2 若两个正实数x,y满足x^2+2xy-3y^2=0,求x^2+xy+y^2/x^2-xy+y^2 当x-y=2xy时,求4x-3xy-4y/xy