已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x))

已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 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 已知/X-Y-1/+(XY+3)的平方=0,求(-2XY+2X+3Y)-(3XY+2Y-2X)-(X+4Y+XY)的值!已知/X-Y-1/+(XY+3)的平方=0,求(-2XY+2X+3Y)-(3XY+2Y-2X)-(X+4Y+XY)的值急! 已知3/(x-y)=1/xy 求(-x-2xy+y)/ (2x+3xy-2y) 已知x-y=4xy,求2x+3xy-2y/x-2xy-y的值 已知x-y=4xy,求x-2xy-y分之2x+3xy-2y的值! 已知x-y=3xy,求5x+2xy-5y/x-4xy-y的值 已知(x+1)²+|y-1|=0,求2(xy-5xy²)-(3xy²-xy)得值 已知x-y=3,xy=1,求（-2x+2x+3y)-(3xy+2y-2x)-(x+4y+xy) 已知X^2+xy-4y=-1,y^2+xy-4x=-3,求x+y的值 已知1/x+1/y=4,求4x-2xy+4y/x+3xy+y的值 已知X+Y=3,XY=-1,求2(X-Y)^4-9(X-Y)^2+12XY 已知1/x-1/y=3,求(3x+4xy-3y)/(x-2xy-y)的值 已知1/x-1/y=3,求3x-2xy-3y/x+4xy-y 已知 1/x-1/y=5.求(2x+4xy-2y)/(x-3xy-y) 已知xy^2=-2,求-xy（x^2y^5-xy^3-y)的值. 已知xy^2=-2 求-xy(x^2y^5-xy^3-y)