## Precalculus (6th Edition) Blitzer

The general formula to find the sum of the first n term of a Geometric sequence is given as: $S_{n}=\dfrac{a_1(1-r^n)}{(1-r)}$
The general formula to find the sum of the first n term of a Geometric sequence is given as: $S_{n}=\dfrac{a_1(1-r^n)}{(1-r)}$ In order to calculate the sum of the first n terms of a Geometric sequence we will multiply the first term $a_1$ by the common difference between $1$ and the nth power of the common ratio; we then divide the result by the difference between $1$ and the common ration $r$.