已知 X² - XY=21,XY-Y²=-2,分别求式子X²-Y²与X²

已知x²-xy,xy-y²=－12,分别求式子x²-y²与x²-2xy 已知x²-xy=21,xy-y²=-12,分别求式子x²-y²与x²- 已知2x-y=10,求式子[(x^2+y^2)-(x-y)^2+2y(x-y)]/4y (4xy-2y²)/4 已知x:y=3:2,求(x²+3xy)/(xy+2xy) 已知x/y=3,求(x²+2xy-3xy²)/(x²-xy+y²) 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 已知y=2x,求(x²-xy-2y²)分之(x²+2xy+y²) 已知x/y=3,求x²+2xy-3y²/x²-xy+y² 已知x/y=2,求x²-xy+3y²/x²+xy+6y²的值 已知y分之x=3,求x²-xy+y²分之x²+2xy-3y² 已知X²+Y²+X²Y²-4XY+1=0 求:（X-Y)^2008-(XY)^2 已知x/y=3,求x²+2xy-3y²/x²-xy+y²的值