X-Y=5,X2+Y2=19,求xy的值
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
若X2+Y2-2X-6Y+10=0 ,求(x2-y2)/xy的值
正数xy满足x2-y2=2xy,求x+y分之x-y的值
已知:x=3,y=-5,x2-2xy+y2/x2-y2的值是
设x,y为实数,且x2+xy+y2=1,求x2-xy+y2的值的范围
已知X2-2x+y2+6y+10=0,求(x2-2xy)/(xy+y2)的值
正整数x,y满足x2-y2=2xy,求x-y/x+y的值
整数x,y满足x2-y2=2xy,求x-y/x+y的值
已知x≠y ,x2-x=3 ,y2-y=3 ,求代数式x2+xy+y2 的值.
已知x2+y2=20,x2+xy-2y2=2(x+2y),求x+y的值
已知x-y+1,X2+Y2=25 求(x+y)2和x2-xy+y2的值
x(x-1)-(x2-y)=-3,求x2-y2-2xy的值