Question

quero a conta da pg.3.12.48.192

Answer 1

A razão da PG que chamamos de q, será:

$q= \frac{a_{2}}{a_{1}}= \frac{12}{3}=4 \\ \\ S_{n}= \frac{a_{1}(1-q^{n})}{1-q} \\ \\ S_{4}= \frac{3.(1-4^{4})}{1-4}= \frac{3.(-255)}{-3}=255$