已知x+y=3,xy=-12,x^2-xy+y^2

已知x+y=3,xy=-12,x^2-xy+y^2 已知:x/y=-2,求x^2-2xy-3y^2/x^-6xy 已知X+Y=3,XY=-1,求2(X-Y)^4-9(X-Y)^2+12XY 由已知x+y=-2,xy=3那么2(x+xy)-[(xy-3y)-x]-(-xy)等于多少? 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-xy=20,xy-y=12,则x-y= ,-2xy+x+y= 已知x-xy=20 xy-y=12,则x-y=（ ）,x+y-2xy=（ ）. 已知:x-xy=20,xy-y=12,则x-y=...,-2xy+x+y=... 已知x+xy+y=3,则(3x+2xy+3y)/(2x+xy+2y)= 已知x-xy =21,xy-y=-12,分别求式子x-y与x-2xy +y 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= 已知x+y分之xy=2,那么3x-5xy+3y分之3xy-x-y= 已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= 已知xy/x+y=3,求2x-3xy+2y/-x+3xy-y的值 已知xy/x+y=3,求2x-3xy+2y/-x+3xy-y的值 已知x-y=3xy,求分式3x+2xy-3y/x-2xy-y的值 已知y=3xy+x,求代数式2x+3xy-2y/x-2xy-y的值