Question

Calcular a soma dos 100 primeiros termos da PA (3,7,11,15,........)

Answer 1

a1=3
r=7-3
r=4
a100= a1+(n-1).r
a100=3+(100-1).4
a100=3+99.4
a100=3+396
a100=399

S100=(3+399).100/2
S100=402.100/2
S100=40200/2
S100=20100