Question

calcule quantos termos tem a p.g( 625,125,25,...1/5)​

Answer 1

usando a formula do termo geral da pg $an=a_{1} . q^{(n-1)}$

substituindo...

$\frac{1}{5} =625 . \frac{1}{5}^{(n-1)}\\\frac{1}{5} =5^{4} . \frac{1}{5}^{(n-1)}\\\frac{1}{5} =5^{4} . \frac{1}{5^{(n-1)}}\\\frac{1}{5} = \frac{1}{5^{(n-5)}}\\ 5^{(n-5)} = 5$

logo...

$n-5=1\\n=1+5\\n=6$