Question

calcule a soma dos 14 primeiros termos da p.a.( 25, 28,31, 34,..)

Answer 1

Bom dia.
an=?
a1=25
r=3
n=14

an=a1+(n-1)r
an=25+(14-1)3
an=25+13*3
an=64

sn=(a1+an) *n/2
s14=(25+64)*14/2
s14=89*14/2
s14=623