page11
Tn=(1²+1+2²+2+3²+3+...+n²+n)/2
= (1²+2²+3²+...+n²)/2
+ (1+2+3+...+n)/2
= Sn/2 + (n²+n)/4
T(n-1)= (Sn-n²)/2 +((n-1)²+n-1)/4
= Sn/2 -n²/2 +(n²+1-2n+n-1)/4
= Sn/2 -n²/4 -n/4
= Sn/2 -(n²+n)/4
Tn35
20
10
4
1
15
10
6
3
1
n
5
4
3
2
1