问答题设f(lnx,)=,求f(x,y).
问答题设f(x+y,)=x2-y2,求f(x,y).
问答题设f(x+y,x-y)=x2-y2-xy,求f(x,y).
问答题求下列函数定义域D:z=√ln(xy)+.
问答题求下列函数定义域D:z=+.