用等价无穷小替换和洛必达法则,原式=lim(x→0)(x-e^x+1)/(x(e^x-1))=lim(x→0)(x-e^x+1)/x^2=lim(x→0)(1-e^x)/(2x)=-1/2lim(x→0)(e^x-1)/x=-1/2