-4x^2*(1/2xy-y^2)-3(xy^2-2x^2y)

XY(XY+3)+(XY+4)+4(X+Y+1)-(X+Y+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 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1 x-y=1,xy=2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= 因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) 化简：3x^2-[5xy-(x^y-3xy)+4x^2y-8xy] 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 x²-y²+5x+3y+4（x+y-2xy)(x+y-z)+(xy-1）² xy-2{xy-[3x^2y-(4xy^2+0.5xy)]+4x^2y}+6xy^2 （X-3xy+4xy-y）-[-2x-2（xy-3/2xy）-y]+6xy的过程 计算3xy[2xy-x(y-2)+x-1] （-3x^y+2xy)-( )=4x^+xy 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) 化简求值x-4y/2x-7xy+3y×x-2xy-3y/2x+3xy-2y÷3x-6y/4x-4xy+y,其中：x=1999,y=-1