先对x求导再对y求导怎么表示答:f(x,y)先对x求导再对y求导:fxy(x,y),先对y求导再对x求导:fyx(x,y),若fxy(x,y),fyx(x,y)在点(x,y)都连续,则有fxy(x,y)=fyx(x,y),反过来,fxy(x,y)和fyx(x,y)相等或不相等。
f(x/y)对x,y求导相等吗答:f(x,y)先对x求导再对y求导:fxy(x,y),先对y求导再对x求导:fyx(x,y),若fxy(x,y),fyx(x,y)在点(x,y)都连续,则有 fxy(x,y)=fyx(x,y),反过来,fxy(x,y)和fyx(x,y)相等或不相等,不能说明什么问题.