作者rebe212296 (绿豆冰)
看板trans_math
标题[微分]偏导数
时间Wed May 8 15:24:40 2013
1.
Let f:R^2→R be defined by f(x,y)=√|xy| for all (x.y)属於R^2
Show that f_x and f_y both exist on R^2 and continuous on R^2\{(0,0)}
but f is not differentable at (0,0).
2.
Let f:R^2→R be defined by f(x,y)=[xy(x^2-y^2)]/(x^2+y^2) if(x,y)≠(0,0)
and f(x,y) = 0 if(x,y)=(0,0)
Show that f_xy(0,0) and f_yx(0,0) both exist but are not equal.
请问以上两题怎麽解? 谢谢!
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