limX→1 X的三次方减1分之X的4次方减1

题目

limX→1 X的三次方减1分之X的4次方减1

答案

原式=lim(x²+1)(x+1)(x-1)/(x-1)(x²+x+1)
=lim(x²+1)(x+1)/(x²+x+1)
=4/3