已知x-3y=2,x+y=5,则x2-2xy-3y2=______.
已知x+y=4,xy=2,则x2+y2+3xy=______.
已知xy=3,x2+xy-2y2=2(x+2y),且x≠-2y,则x+y=______.
已知x+y=5,xy=3 则x2+y2=______.
已知:x=3,y=-5,x2-2xy+y2/x2-y2的值是
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
已知x2+4x+y2-2y+5=0,则x2+y2=______.
已知实数x,y满足x2+xy+y2=3,则x2-xy+y2的最小值
已知x+y=4,xy=2,求x2+y2+3xy的值.
已知x+y=-5,xy=6,则x2+y2=______.
已知xy=-3,x+y=-4,则x2+3xy+y2值为______.
分解因式2x2-xy-6y2+7x+7y+3=______.
已知实数x、y满足2x2-7xy+3y2=0,求x:y