Question

Write an equation for the nth term of each geometric sequence:
5, 10, 20, 40,​

Answer 1

a(n) = 5*2^(n-1)

Explanation:

The nth term of a geometric series is given by the relation :

a(n) = ar^(n-1)

Where, a = first term ; r = common ratio ; a(n) = nth term of the series.

Given the series : 5, 10, 20, 40,​

First term, a = 5

Common ratio = a2/ a1 = a3/a2

Common ratio = 10/5 = 20/10

Common ratio = 2 = 2

Hence, nth term =

a(n) = 5*2^(n-1)