Question

Termo geral:

An= A1.q^n-1


(1/27,1/9,1/3,..., 729)

n=?


729=1/27.3^n-1


Não consigo continuar a conta.

Answer 1

$729=\left(\frac{1}{27}\right).3^{n-1}\\\\\\3^6=\left(\frac{1}{3^3}\right).3^{n-1}\\\\\\3^6~=~3^{-3}~.~3^{n-1}\\\\\\3^6~=~3^{n-1+(-3)}\\\\\\3^6~=~3^{n-4}\\\\\\6~=~n-4\\\\\\n~=~6+4\\\\\\\boxed{n~=~10~termos}$