lim x趋近1 (三次根号下x -1)/(根号下x -1)
=lim x趋近1 (根号下x +1）（x-1)/(三次根号下x^2+ 三次根号下x+1)(x-1)
=lim x趋近1 (根号下x +1）/(三次根号下x^2+ 三次根号下x+1)=2/3