x^2+xy+y^2=2013,求x^2-xy+y^2的最大值

x^2+xy+y^2=2013,求x^2-xy+y^2的最大值 已知x+y=2013,xy=2012,求xy-2(x+y)的值 x^2+xy+x=36,y^2+xy+y=20,求x+y. 若x^2+xy+y=14,y^2+xy+x=28,求x+y 如果x^2+xy+y-14,y^@+xy+x=28,求x+y的值. f(xy,x-y)=x^2-xy+y^2.求f(x,y) y'=-2xy;求f(x). x-2+y=100求Xy y/x=ln(xy) 求dy/dx(xy-y^2)/(xy+x^2) 已知x-xy=8,xy-y=-9,求x+y-2xy的值 1-2/x+y=xy,4y+6x=xy.求xy的解? 当x-y=2xy时,求4x-3xy-4y/xy x^2-y^2=xy 求x/y, x+y+2xy=83求x+y=? 若1/x-1/y=2,求3x-2xy-3y/x-xy-y的值3x-2xy-3y/x-xy-y 不好意思，是3x-2xy-3y/x-2xy-y f(x+y,x-y)=(x^2-y^2)/2xy,求f(x,y)! 正数x,y满足x-y=2xy,求x-y/x+y的值. f(x+y,x-y)=2xy(x-y),求f(x,y)