## Precalculus (6th Edition) Blitzer

In an arithmetic sequence, the digits increase or decrease in a specific pattern. The difference between the digits is called the common difference. If the sequence increases, it will have an increasing order and if it decreases it will have a decreasing order. In the given situation, the theater has an increasing form of the sequence if we move backwards. The seats in every row are increasing by 1, i.e. the common difference is $d=1$. Example: A theater has 25 rows. It has 30 rows in the first row, then 31 seats in the second row, and then 33 seats in the third row as we move backwards. This formation of seats is an arithmetic progression or sequence. So, this is viable.