已知xy=-1,求3xy^2(x-x^3y^2-1/2x^2y)的值

已知（x+1）*（x+1）=-Iy-1I,求2（xy-（5xy）*（5xy））-3（（xy）*（xy）-xy） 已知(x+1)²+|y-1|=0,求2(xy-5xy²)-(3xy²-xy)得值 已知3/(x-y)=1/xy 求(-x-2xy+y)/ (2x+3xy-2y) 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) 已知x:y=3:2,求(x²+3xy)/(xy+2xy) .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 已知x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+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 已知xy为正整数,3xy=2x+3y+5.求xy=? 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) 已知X+Y=3XY,求2X+2Y-XY除以X+Y+2XY的值,要算理.已知X+Y=3XY,求2X+2Y-XY除以X+Y+2XY的值,要算理. 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:x/y=-2,求x^2-2xy-3y^2/x^-6xy 已知x(x-1)-(x^2-y)=-3求（二分之y-x+2xy)-xy 快, 已知x(x-1)-(x²-y)=-3,求(x²y+xy²)÷xy-2y 已知(x-3)^2+丨3y+1丨=0.求3x^2y-[2xy-2(xy-3/2)+xy]+3xy^2的值 已知x-y=3,xy=1,求（-2x+2x+3y)-(3xy+2y-2x)-(x+4y+xy)