Question

Quantos elementos tem a PG. (8,32,...2^31)

Answer 1

an = a1 * q^n-1
2^31 = 8 * 4^n-1
2^31 = 2^3 * (2^2)^n-1
2^31 / 2^3 = 2^2n - 2
2^28 = 2^2n-2
2n - 2 = 28
2n = 28 + 2
2n = 30
n = 30/2
n = 15