已知f(x,y)=x2+y2,求f(x-y,√xy)
求函数f(x,y)=x2+xy+y2-6x-3y的极致
已知实数x,y满足1≤x2+y2≤4,求f(x,y)=x2+xy+y2的最大值和最小值
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)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
已知x+y=8,xy=12,求x2+y2;(x-y)2的值
已知x>y>0,且xy=1,求 (x2+y2)/(x-y)的最小值,
已知实数x、y满足2x2-7xy+3y2=0,求x:y
已知x(x-1)-(x2-y)=-3,求x2+y2-2xy的值
求函数f(x,y)=(x2+y2)2-2(x2-y2)的极值
已知x2+4y2+x2y2-6xy+1=0,求 x4-y4/2x-y 乘 2xy-y2/xy-y2 除以(x2+y2/x