问答题
设当xy为有理数时f(x,y)=0,否则f(x,y),求
求证,设f,g∈L1[a,b],F(X)=∫axfdm,G(x)=∫axgdm,则
求证,设f∈L1[a,b],则∫abf(x)dx∫axf(y)dy=
设f∈L1[0,a],g(x)=,则∫0agdm=∫0afdm