Question

Calcule a soma da PA(3,5,7,9,...)de último termo a 80

Answer 1

a1=a2-r
3=5-r
r=5-3
r=2

a80=a1+79r
a80=3+79.2
a80=161

Sn=(a1+an).n/2
S80=(3+161).80/2
S80=(164).80/2
S80=13120/2
S80=6560 <<<