已知x2+xy=7 y2+xy=2 求x-y的值

已知X/Y=2/7, 求X2-3XY+2Y2/2X2-3XY+7Y2的值 已知x/y=2/7,求分式(x2-3xy+2y2)/(x2-2xy+y2)的值 已知x/y=2/7,求分式x2-3xy+2y2/x2-2xy+y2的值 已知x2+xy=7 y2+xy=2 求x-y的值 已知x2-3xy=-5,xy+y2=3,求x2-2xy+y2. 已知x/y+y/x=2,求(x2+xy+y2)/(x2-4xy+y2)的值 已知x2+y2+4x-2y+5=0,求x2+2xy+y2值 已知x满足2x2+4x+y2=2xy-4 求：xy 已知y/x=1/2,求(x2+2xy+y2)/﹙x2-xy-2y2)的值. 已知X2-2x+y2+6y+10=0,求（x2-2xy）/(xy+y2)的值 已知x/y=3/5,求 (x2-xy+2y2)/(x2+2xy-y2)的值 已知x+y=4,xy=2,求x2+y2+3xy的值. 已知x2+y2=7,xy=-2,求5x2—3xy—4y2—11xy—7x2+2y2的值 已知X2+y2=7,Xy=-2,求多项式5X2一3Xy-4y2-11Xy-7X2+2y2的值. 已知x2+y2 =7,xy=-2.求5x2 -3xy-4y2 -11xy-7x2 +2y2 已知实数x、y满足2x2-7xy+3y2=0,求x：y (1)已知X+Y=7 XY=2 求 X2次方+Y2次方 已知x(x-1)-(x2-y)=-2求x2+y2-4xy的值