Question

Qual o número de termos da PG

Answer 1

$q= \frac{a_{2}}{a_{1}}= \frac{256}{512}= \frac{1}{2} \\ \\ logo \\ \\ a_{n}=a_{1}.q^{n-1} \\ \\ \frac{1}{1024}=512.( \frac{1}{2})^{n-1} \\ \\ 2^{-10}=2^{9}.2^{-n+1} \\ \\ 2^{-10}=2^{-n+10} \\ \\ -n+10=-10 \\ n=20$