Question

Calcule quantos termos tem a PG finita
an=448
a1=7
q=2
n=?

Answer 1

$an=a1.q^{n-1} \\ \\ 448=7.2^{n-1} \\ \\ 2^{n-1}= \frac{448}{7} \\ \\ 2^{n-1}=64 \\ \\ 2^{n-1}=2^6 \\ \\ n-1=6 \\ \\ n=7$