## Precalculus (6th Edition) Blitzer

General equation is: $a_n=9+2(n-1)$; $47$
Formula to calculate the nth term of an arithmetic sequence is: $a_n=a_1+d(n-1)$ Here, $a_1:$ First term and $d=$ common difference Since, we have $a_1=9$ Then, our General equation is: $a_n=9+2(n-1)$ $a_{20}=9+2(20-1)=9+38=47$