## Precalculus (6th Edition) Blitzer

The summation notation $\sum$ signifies the sum as $\sum_{i=p}^q a_i$ Here, $a_i$ are the terms to be added and $i$ shows the index of the summation and $p$ denotes the lower limit of summation and $q$ is the upper limit of the summation. $\sum_{i=p}^q a_i=a_p+a_{p+1}+......a_{q-1}+a_q$