dingpeng If <bblatex>f:R\rightarrow R</bblatex> satisfies: 1.<bblatex>f(a+b)=f(a)+f(b);</bblatex> 2.<bblatex>f(ab)=f(a)f(b);</bblatex> 3.<bblatex>f(1)\not= 0;</bblatex> then <bblatex>f(x)=x, \forall x\in R.</bblatex> 结论对吗？如果没有告知<bblatex>f</bblatex>连续？
