2x－3＝y xy=209 求xy?

2x－3＝y xy=209 求xy? 3X^2+XY+Y=15 求XY. 当x-y=2xy时,求4x-3xy-4y/xy xy^2=-3,求-xy(x^2y^5-xy^3-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) 已知x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+y^2 已知x:y=3:2,求(x²+3xy)/(xy+2xy) 设x²＋xy=3,xy＋y²＝2,求2x²－xy－3y²的值 x的平方－3xy=-5.xy+y的平方＝3,求x的平方－2xy+y的平方,的值 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 已知xy为正整数,3xy=2x+3y+5.求xy=? 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 当x=3,y=3分之1时,求代数出3xy-[2xy-2(xy-2分之3xy)+xy]+3xy的值 已知xy/x+y=3,求2x-3xy+2y/-x+3xy-y的值 xy/x+y=3求2x-3xy+2y/3xy-x-y的值 已知xy/x+y=3,求2x-3xy+2y/-x+3xy-y的值