Answer:
4
Explanation:
The sum of the first n terms of a geometric series is:
S = a₁ (1 − r^n) / (1 − r)
Given n = 6, S = 15624, and r = 5:
15624 = a₁ (1 − 5^6) / (1 − 5)
a₁ = 4
5.8m questions
7.6m answers