Find the 9th term of the geometric sequence whose common ratio is 13 and whose first term is 7.

Answer 1

a1 = 7 = first term of the geometric sequence

r = 13 = the common ratio of the geometric sequence

a9 = ? = the 9th term of the geometric sequence

general formula for the nth term of a geometric sequence is

an = a1(r^(n-1))

if n=9, substitute n with 9 to get

a9 = 7(13^8) = 5,720,225,047

getting close to 6 billion