Question

Calcule a soma dos 5 primeiros termos de P.G (1,4...)

Answer 1

$q=\frac{a2}{a1}=\frac{4}{1}=4\\a1=1\\\\S=\frac{a1(q^n-1}{q-1}=\frac{1(4^5-1)}{4-1}=\frac{1024-1}{3}=\frac{1023}{3}=\boxed{341}$