Find the first term of the sequence 5,15,45,135 that exceeds 20,000

Answer 1

a = 5
r = 3
5*3^n > 20000
3^n > 4000
n > log4000/log3 = 9.73
So the 9 term will exceed 20,000
check:
a8 = 5*3^7 = 10935
a9 = 5*3^8 = 32805

Answer 2

9term