Question

qual o numero de termos da PG (512,256,128,...1/1024) ?

Answer 1

Utilize a Fórmula do Termo Geral da PG:

$a_n=a_1*q^{n-1}\\ \\ 512*(\frac{1}{2})^{n-1}=\frac{1}{1024}\\ \\ (\frac{1}{2})^{n-1}=\frac{1}{1024}\div 512\\ \\ (\frac{1}{2})^{n-1}=\frac{1}{1024}*\frac{1}{512}\\ \\ (\frac{1}{2})^{n-1}=\frac{1}{524288}\\ \\ (\frac{1}{2})^{n-1}=(\frac{1}{2})^{20}\\ \\ n-1=20\\ \\ n=21$