把-1/x放到根号内,所以lim(x→-∞) 1/x×√[x^3/(x-1)]=-lim(x→-∞) √[x/(x-1)] 分子分母同除以x=-lim(x→-∞) √[1/(1-1/x)]=-1
将1/x 乘到根号内,变成1/x^2 原式为limx→-∞ √x/(x-1) =√1/(1-1/x) =√1 =1
limx→-∞(1/x)*√[x^3/(x-1)]=令t=1/xlimx→-0t*√[1/t^3/(1/t-1)]化简=limx→-0√(1/1-t)=1