极限lim n(2n-1）分之1+2+3+...+n=_数学解答

极限lim n(2n-1）分之1+2+3+...+n=

人气：357 ℃　时间：2020-03-25 05:58:01

解答

=lim n(n+1)/2n(2n-1)
=lim (n+1)/(4n-2)
=1/4lim n(n+1)/2n(2n-1)这一步怎么弄的啊1+2+3+……+n=n(n+1)/2