Question

quantos elementos tem a pg(8,32,..2

Answer 1

an = a1 x q^n - 1                                                                                                      

2^31= 8 x 4^n - 1

2^31 = 2^3 x 2^ 2n - 2

2^31=  2^3 + 2n - 2

2^31 = 2^2n+ 1

2n + 1 = 31

2n = 31- 1

2n = 30

n = 30/ 2

n= 15