Question

if TN =2n+n,then find sn​

Answer 1

Answer:

Tn=2n+n

T1=a=2+1=3

T2=2(2)+2=4+2=6

a=3

d=3

Sn=ⁿ/2(2a+(n-1)d)=ⁿ/2(6+3n-3)=(3n²+3n)/2