Exercise 10 Page 202

Explicit equations for arithmetic sequences follow a specific format. In this form, $a_1$ is the first term of the sequence, $d$ is the common difference, and $a_n$ is the $n\text{th}$ term. In the given sequence, the first term is $a_1=1.$ Let's pay close attention to the pattern in order to determine the common difference $d.$ The common difference is $\text{-}1.$ Therefore, by substituting $a_1=1$ and $d=\text{-}1$ into the explicit equation and simplifying, we can find the formula for this sequence. We found the equation for the $n\text{th}$ term of the given arithmetic sequence. This equation can be used to find any term of the sequence. To find $a_{25},$ the $25\text{th}$ term, we substitute $25$ for $n.$ The $25\text{th}$ term of the sequence is $\text{-}23.$