设f(x,y)=(xy)/(x^2+y) ,则 f(xy,x/y)=______ 。
举一反三
- 已知f(x+y,xy)=x^2+y^2,则f(x,y)=()
- 设函数z=f(x,y)=xy/(x2+y2),则下列结论中不正确的是() A: f(1,y/x)=xy/(x+y) B: f(1,x/y)=xy/(x+y) C: f(1/x,1/y)=xy/(x+y) D: f(x+y,x-y)=xy/(x+y)
- 设f(x,y,z)=xy^2z^3,且z=(x,y)由方程x^2+y^2+Z^2-3xyz=0确定,求αf/αx
- 设f(u)连续,且du(x,y)=f(xy)(ydx+xdy),则u(x,y)=______.
- 设 $D=\{(x,y)|x^2+y^2\le 4, y\ge 0\}$,则二重积分 $\iint_D xy^2dxdy=$______ .