1-x-2Xy-y=1-()

已知x+y=1,xy=-2,则x²y+xy²-2xy 1-2/x+y=xy,4y+6x=xy.求xy的解? 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+3xy)=-xy-1/3y^2 （x+2y-3xy)-(-2x-y+xy),其中x+y=1/2,xy=-1/2 xy^2-e^x+e^y=1 求y' 是xy^2 不是xy 因式分解（x+y-2xy)(x+y-2)+(xy-1)^2设x+y=a,xy=b, 已知3/(x-y)=1/xy 求(-x-2xy+y)/ (2x+3xy-2y) 已知xy-x-y=11,求(xy-1)^2+(x+y-2)(x+y-2xy)的值. 已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= x+y=1,xy=-2求(x²+y²+xy)/(x²+y²-xy) .(x+y-2)(x+y-2xy)+(xy-1)^2 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 1-x-2Xy-y=1-() 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 x-y=1,xy=2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值