Question

Quantos termos tem a P.G (7,21,...,1701) ?

Answer 1

$an=a1*q^{ n-1 }\\ 1701=7*3^{ n-1 }\\ \frac { 1701 }{ 7 } =3^{ n-1 }\\ \\ 243=3^{ n-1 }\\ 3^{ 5 }=3^{ n-1 }\\ 5=n-1\\ 5+1=n\\ 6=n$