Question

Find the 13th term of the geometric sequence 5, 10, 20, ...5,10,20,...

Answer 1

a13 = 20,480

Explanation:

The first term is a1 = 5, and the common ratio is ...

r = 10/5 = 2

The generic term is ...

an = a1·r^(n-1)

an = 5·2^(n-1)

Then the 13th term is ...

a13 = 5·2^(13 -1) = 5·4094

a13 = 20,480