A geometric series is a+ar+ar2+…a + ar + ar^2 + \dotsa+ar+ar2+…
Prove that the sum of the first n n\,n terms of the series is
Sn=a(rn−1)r−1 S_n = \frac{a(r^n - 1)}{r - 1} Sn=r−1a(rn−1)38 exam-style questions on AQA A Level Maths 1.7.5 Geometric sequences and series (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.