作业帮数列｛n²｝前n项和推导过程
来源：学生作业帮助网 编辑：作业帮 时间：2024/11/20 23:30:17
xPJ@RIt IMѿ*3 h*Z( qΝnZu_pm7s=uxv?xЋ V +6 ]?_>O/B`<UD@[z % C^av];p>RR؉
1TgAYj&2
0cP, pR3S+
:Eu\_*
Q= wxQD
'6M ž`/C[ʳ_WAKwQއY]5*C#~H0v0 Aʘۆ2) r,sqaShom&Jw,?BYA4EpLT0ȥ$3 ?
数列｛n²｝前n项和推导过程
数列｛n²｝前n项和推导过程
数列｛n²｝前n项和推导过程
n^2 = n(n+1) -n
= (1/3)[ n(n+1)(n+2)- (n-1)n(n+1) ] - (1/2)[n(n+1) - (n-1)n]
∑(i:1->n) i^2
=∑(i:1->n) {(1/3)[ i(i+1)(i+2)-(i-1)i(i+1) ] - (1/2)[i(i+1) - (i-1)i] }
=(1/3)n(n+1)(n+2) -(1/2)n(n+1)
= (1/6)n(n+1)(2n+1)
