2 5 8 11. Does anyone know how to derive the formula Sn n 2 2a n - 1 d. Now apply the formula 2 for the sum of the first n terms of an arithmetic progression.
The formula for the n -th partial sum Sn of a geometric series with common ratio r is given by.
Common difference -4 Derivation of Formulas Let d common difference a 1 first term a 2 second term a 3 third term a m. The formulas for the sum of the arithmetic sequence are given below. Sn n 22a n 1d S n n 2 2 a n 1 d or. S n n 2 a a n 1 d S n n 2 2 a n 1 d The general formula for determining the sum of an arithmetic series is given by.