若x^2+xy=2、y^2+xy=7,则x^2-y^2=

已知xy/x+y=3,则代数式2x-7xy+2y/-x+xy-y的值是多少? 若x+y分之xy=2,则-x+3xy-y分之3x-xy+3y=多少? 若xy/x+y=2,则3x-5xy+3y/-x+3xy-y=?/是分之 若x+y分之xy=2,则-x+3xy-y分之3x-xy+3y=多少? 若xy/x+y=2,则3x-xy+3y/-x+3xy-y= 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= 已知x+y=1,xy=-2,则x²y+xy²-2xy x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________? 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 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 |x-2|+|y-2|=0,求xy=?；|x|=-|y-7|,则xy=? 如果x+y=0,xy=-7,则x^2y+xy^2=? 如果X+Y=10 XY=7则X~2Y+XY~2=? 若 x+y=5,xy=-50 则x^2y+xy^2 =( ) 若x+y=3,xy=-2 ,则2xy-（x+y）= 若x-y=1,xy=5,则x^2y-xy^2＝ 若x-y/x+y=2,则x2+2xy+y2/4xy=多少 若x/y=2则x的平方-xy/xy+y的平方的值