GP SumEasyQuestion 210014
Question
The sum of first n terms of a GP with first term a and ratio r (r ≠ 1) is:
- Aa(rⁿ − 1)/(r − 1)Correct
- Ba(rⁿ + 1)/(r + 1)
- Cnaʳ
- Da/(1 − r)
Correct answer
a(rⁿ − 1)/(r − 1)
Explanation
GP sum formula: Sₙ = a(rⁿ − 1)/(r − 1) for r > 1, or equivalently a(1 − rⁿ)/(1 − r) for r < 1.