已知x，y都为正整数，(x)^2+(y)^2=2009，求x+y的值.

已知x、y是.正整数, .-|||-^2+(y)^2=2009 ,求 x+y

已知(x,y)=(e)^x+(y-2)arcsin sqrt ({x)^2+(y)^2}，求(x,y)=(e)^x+(y-2)arcsin sqrt ({x)^

设 (x+y,x-y)=2((x)^2+(y)^2)(e)^(x^2-{y)^2}, 则 _(x)(x,y)-(f)_(y)(x,y)= __

2.已知 dfrac (x)(x+y)=dfrac (1)(3) ,求 dfrac ({x)^2-(y)^2}(2xy+{y)^2} 的值.

求旋转曲面=(x)^2+(y)^2在点=(x)^2+(y)^2处的法线方程A.=(x)^2+(y)^2B.=(x)^2+(y)^2C.=(x)^2+(y)^2D

1.函数 (x+y,xy)=(x)^2+(y)^2-xy, 则 f(x,y)=

已知x，y都是正数，且x≠y，求证：（1）(x)/(y)+(y)/(x)＞2；（2）(2xy)/(x+y)＜sqrt(xy)．已知x，y都是正数，且x≠y，求证

6.讨论下列函数的连续性:-|||-(1) (x,y)=dfrac ({x)^2-(y)^2}({x)^2+(y)^2}-|||-(2) (x,y)=dfrac

求(x,y)=(x)^2+(y)^2+6x-12y+5的极值.求的极值.

[题目]-|||-求函数 (x,y)=(x)^2(2+(y)^2)+yln y 的极值.