Question

1) A partir da PG (80, 40, 20, 10, ...), calcule a soma de todos os termos dessa PG.

Answer 1

$q=\dfrac{40}{80}=\dfrac12\\\\S_\infty=\dfrac{a_1}{1-q}\\\\\\S_\infty=\dfrac{80}{1-\frac12}=\dfrac{80}{\frac12}=160$