Question

Calcule a soma dos 20 primeiros termos da PA (2,6,10...,)​

Answer 1

Resposta:

R=4

a1=2

n=20

an=a1+(n-1).r

an=2+(20-1).4

an=2+19.4

an=2+76

an=78

Sn=n(a1+an)/2

Sn=20(2+78)/2

Sn=20.80/2

Sn=1600/2

Sn=800