Answer:
3 × 5 ^ n
Step-by-step explanation:
since the series is exponential, the ratio between adjacent terms is 5.
nth term of geometric/exponential series is given by:
nth term = first term × (ratio)^(n-1)
= 15 × 5^ (n-1)
= 15 × 5^n × 5^-1
= 3× 5^n
