x^2-6xy+9y^2-1=

1-2/x+y=xy,4y+6x=xy.求xy的解? 已知1/x-1/y=2,求3x+7xy-3y/2x-3xy-2y答案是1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/7 谁能帮我解释一下=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy) 是怎 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 3x^2-xy /9x^2-6xy+y^2,其中x=1/2,y=-2/3 化简求值x-4y/2x-7xy+3y×x-2xy-3y/2x+3xy-2y÷3x-6y/4x-4xy+y,其中：x=1999,y=-1 -3x^2y+6xy^2-9xy=( )(x-2y+3) x^2-6xy+9y^2-1= 解方程组：xy/x+y=-6(1) 2xy/x+2y=12(2) (x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y)答案应为-2x-x*x-3x， [6xy-3(xy-1/2x的平方y]/3xy=? ①(9x²y-6xy²)÷3xy ②(3x²y-xy²+2分之1xy)÷(-2分之1xy) 解方程组：{x²+xy-2y²=0,x²+6xy-9y²=1 [6xy-3(xy-2分之1x^2y]除3xy,其中x=2002,y=2003 [6xy-3(xy-1/2x的平方y]/3xy=?其中x=2008,y=2009 已知x-xy=8,xy-y=-9,求x+y-2xy的值 已知x+y=1,xy=-2,则x²y+xy²-2xy 已知1/x - 1/y = 2,求3x+7xy-3y / 2x-3xy-2y的值1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/71/x-1/y=2到(y-x)/xy=2 是怎么变化的.. 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