Question

Calcule a soma dos 26 primeiros termos da P.A. (1,2,9,...

Answer 1

an=26
a1=1
r=7

An= a1+(n-1).r
a26=1+(26-1).7
a26=1+25.7
a26=175

sn= (a1+an).n/2


sn=(1+175).7/2

sn= 1232/2

sn=616