根据洛笔答法则,lim((sinx+xf(x))/x3)=lim((cosx+f(x)+x·f'(x))/3x²)若x→0时这个极限存在,则必有lim cosx+f(x)+x·f'(x)=0则cos0+f(0)=0f(0)=-1再进一步用洛笔答法则得lim((cosx+f(x)+x·f'(x))/3x²)=li...