如果x-2y=7,xy=3,则2xy-4x+2x+5=

如果X-2Y=7,XY=3,则2XY-4Y+2Y+5=( ) 如果x-2y=7,xy=3,则2xy-4y+2x+5 如果x-2y=7,xy=3,则2xy-4x+2x+5= 如果x+y=0,xy=-7,则x^2y+xy^2=? 如果X+Y=10 XY=7则X~2Y+XY~2=? 如果x-y＝2,xy=3,则x²y-xy²=几 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 如果x+y=4,xy=-1,那么多项式2x+3y-3xy+4xy-3x-4y+7的值为 （-3x^y+2xy)-( )=4x^+xy 已知xy/x+y=3,则代数式2x-7xy+2y/-x+xy-y的值是多少? 如果xy/x+y=2,那么3x-5xy+3y/-x+3xy-y=? 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= 当x-y=2xy时,求4x-3xy-4y/xy 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 已知x+y=4,xy=2,求代数式2(3x+2xy)+(2xy+3x+2y)-(4xy-7y)的值 x+y=8,xy=-2,求(5xy+4x+7y)+(6x-3xy)-(4xy-3y)的值 已知x-y=8 xy=7,则3xy-2x+2y+4(y-x)²=?