F(x)在x=0附近有定义,且|f(x)|≤x^2,则有 |f(0)|≤0^2=0,则f(0)=0,f‘（0）=lim(x→0)〖(f(x)-f(0)/x〗 = lim(x→0) f(x)/x对于∀ϵ>0,∃δ=ϵ>0,∀x:|x-0|≤δ,有|f(x)/x-0|=|f(x)/x|≤x^...