Given:
Lee has 3 dog walking customers.
Each month he gains another customer.
To find:
The arithmetic sequence that represents the number of customers he has.
Solution:
Initial number of customers = 3
First term : [tex]a_1=3[/tex]
Each month he gains another customer.
Common difference : [tex]d=1[/tex]
Recursive formula of an AP is
[tex]a_n=a_{n-1}+d[/tex]
where, d is common difference.
Substituting d=1, we get
[tex]a_n=a_{n-1}+1[/tex]
So, the required arithmetic sequence is [tex]a_n=a_{n-1}+1[/tex], where [tex]a_1=3[/tex].
Therefore, the correct option is A.