2x-3=y xy=209

（-3x^y+2xy)-( )=4x^+xy x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________? 当x-y=2xy时,求4x-3xy-4y/xy 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 由已知x+y=-2,xy=3那么2(x+xy)-[(xy-3y)-x]-(-xy)等于多少? f(xy,x-y)=x^2+3xy+y^2,则f(x,y)=? ( )-(x^2+3xy)=-xy-1/3y^2 ( )*3xy=6x^2y+2xy^2 2xy+5y^2+( )=x^2+3xy 3X^2+XY+Y=15 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x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+y^2 已知x+xy+y=3,则(3x+2xy+3y)/(2x+xy+2y)= 已知x-y=3xy,则2x+3xy-2y除以x-2xy-y=? 已知x-y=3xy,则2x+3xy-2y/x-2xy-y= （x+2y-3xy)-(-2x-y+xy),其中x+y=1/2,xy=-1/2 已知x+y分之xy=2,那么3x-5xy+3y分之3xy-x-y= 若x+y分之xy=2,则-x+3xy-y分之3x-xy+3y=多少?