Question

Calculando a soma dos quatro primeiros termos da PG(3,24,192,..),obtemos

Answer 1

✅ A soma dos quatro primeiros termos da PG é $\rm \mathbb{S}_4 = 1755$

 

$\large\begin{array}{lr}\rm \mathbb{S}_n = \dfrac{a_1(q^n - 1)}{q-1} \\\\\rm \mathbb{S}_4 = \dfrac{3(8^4 -1)}{8-1} \\\\\rm \mathbb{S}_4 = \dfrac{3 \cdot 4095}{7} \\\\\rm \mathbb{S}_4 = \dfrac{12\,285}{7} \\\\\red{\underline{\boxed{\boxed{\rm \therefore\:\mathbb{S}_4 = 1755}}}}\end{array}$