Question

The sum of the first 6 terms of a geometric series is 15,624 and the common ratio is 5 what is the first term of the serious?

Answer 1

first term = 4

Explanation:

Sₙ = (a₁ * (1 - rⁿ)) / (1 - r) a₁: first term r: common ratio n: terms

15624 = (a₁ * (1 - 5⁶)) / (1 - 5)

= (a₁ * -15624) / -4

a₁ x (-15624) =15624 x (-4)

a₁ = 4

check: 4+20+100+500+2500+12500 =15624