Question

Calcule a soma dos doze primeiros termos da P.A (-3,-1, 1, 3....)

Answer 1

an=a1+(n-1)r
a12=-3+(12-1)r
a12=-3+11r
a12=-3+22
a12=19

sn=(a1+an)n/2
sn=(-3+19)12/2
sn=16.6=96

resposta 96