Question

A geometric sequence has an initial value of 2 and a common ratio of 3. Which formula would be more practical to use if you were looking find the value of the 19th number in the sequence?

Answer 1

19th term = ar^18

19th term = 774,840,978

Explanation:

First term, a = 2

Common ratio, r = 3

nth term of a geometric sequence = ar^(n-1)

19th term = ar^(19-1)

19th term = ar^18

= 2 × 3^18

= 2 × 387,420,489

= 774,840,978

19th term = 774,840,978