3xy+xy+3+4xy-7化简,已知x=5,y=6

3xy+xy+3+4xy-7化简,已知x=5,y=6 (-3xy+2xy)-(4xy+xy) 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 【x(xy-xy)-y(x-xy)】÷3xy 已知x+y=4,xy=3,则-xy-xy= 已知X+Y=6,xy=3求代数式（5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)的值 已知x+y=3,xy=1,求代数式5xy+4x+7y+6x-3xy-4xy+3y的值. 已知x+y=4,xy=2,求代数式2(3x+2xy)+(2xy+3x+2y)-(4xy-7y)的值 3xy-4xy-（-2xy） 4xy+6xy-3xy=? 3xy-4xy-（-2xy） 化简：3x^2-[5xy-(x^y-3xy)+4x^2y-8xy] -xy(4z-2xy)-(3xy-4z) 化简 xy×(xy)²-3xy x^3y(-4y)^2+(-7xy)^2*(-xy)-5xy^3*(-3x)^2 5x^2y-3xy^2+4xy-14xy^2+4xy-2x^2y（化简） 化简:xy分之3x^2+2xy-xy分之2x^2-xy= 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..