Question

Calcule a 8° termo da PG ( -2, -10, -50, -250, ...)

Answer 1

Vamos começar calculando a razao da PG:

$razao = \frac{a_{n+1}}{a_n}\\\\razao=\frac{a_2}{a_1}\\\\razao=\frac{-10}{-2}\\\\razao=5$

Agora utilizando a equação do termo geral:

$a_n=a_m.q^{n-m}\\\\a_8=a_1.q^{8-1}\\\\a_8=-2\;.\;5^7\\\\a_8=-2\;.\;78125\\\\a_8=-156250$