Question

Calcular a soma dos cem primeiros termos da P.A.(3,7,11...)

Answer 1

r=a2-a1

r=7-3

r=4

an=a1+(n-1).r

a100=3+(100-1).4

a100=3+400-4

a100=3+396

a100=399

sn=n.(a1+an)/2

s100=100.(3+399)/2

s100=100.(402)/2

s100=100×(201)

s100=20.100

espero ter ajudado!

bom dia !