已知x/y=2/7 则x^2-3xy+2y^2 / 2x^2-3xy+7y^2=?1/x+1/y=2 求2x-3xy+2y / 3x+3y+2xy=?已知x/y=2/7 则x^2-3xy+2y^2 / 2x^2-3xy+7y^2=?1/x+1/y=2 求2x-3xy+2y / 3x+3y+2xy=?

已知xy/x+y=3,则代数式2x-7xy+2y/-x+xy-y的值是多少? 已知x-y=8 xy=7,则3xy-2x+2y+4(y-x)²=? 已知x+xy+y=3,则(3x+2xy+3y)/(2x+xy+2y)= 已知x-y=3xy,则2x+3xy-2y除以x-2xy-y=? 已知x-y=3xy,则2x+3xy-2y/x-2xy-y= 已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= 已知xy^2=-2求xy（2x^3y^7+5x^2y 已知x/y=3/4 ,则3xy-2y/2x+4xy=? 已知x+y=6,xy=-3,则x^2y+xy^2=? 已知x+y=5,xy=-3,则x^2y+xy^2, 已知x+y=2,xy=3,则x²+y²-3xy=? 已知x+y=6,xy=-3,则x∧y+xy∧2= 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 已知xy/x+y=2,则代数式3x-5y+8y/-x+3xy-y的值 已知x+y=1,xy=-2,则x²y+xy²-2xy 已知x^2-3xy+2y^2=0 则x/y+x/y= 已知(x+y)/(x-y)=3/2,则(x²+y²)/xy =