求4x^2y-{6xy-2（4xy-2）-x^2y}+1的值,其中x=-1/2,y=1

（X-3xy+4xy-y）-[-2x-2（xy-3/2xy）-y]+6xy的过程 1-2/x+y=xy,4y+6x=xy.求xy的解? 已知x+y=4,xy=-2,求代数式3（xy+2y）-（xy-6x） 已知 x+y＝4,xy＝2,求2xy+4xy+2xy 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 诺x+y=6,xy=4 求(5x-4y-3xy)-(8x-y+2xy) xy-2{xy-[3x^2y-(4xy^2+0.5xy)]+4x^2y}+6xy^2 当x-y=2xy时,求4x-3xy-4y/xy x^+2xy+y^+4=16 x^-2xy+y^=16 求(3xy+6y^)+|x^-(2xy+2y^-3x^)|的值 已知；x+y=4,x-y的绝对值=6,求xy(y的平方+y)-y的平方（xy+2x）-3xy先化简再求值 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 5xy^2-(3xy^2-(4xy^2-2x^2y))+2x^2y-xy^2求 已知x+y=4,xy=-2,求代数式3(xy+2y)-(xy-6x)的值 3(x-y)²-7(x-y)+8(x-y)²+6(x-y)求详细过程（2） 5xy-4x²y-8xy²+3xy-xy²+4x²y x+y=8,xy=-2,求(5xy+4x+7y)+(6x-3xy)-(4xy-3y)的值 已知x+y=6,xy=4,求x^2y+xy^2的值~ (x^2+2xy+y^2-4xy)*(x^2-2xy+y^2+4xy)