Answer: [tex]a_{n}=a_{n-1}-3[/tex] , [tex]n\geq 2[/tex]
Step-by-step explanation:
[tex]a_{1}[/tex] = 18
The common difference = -3
Therefore :
[tex]a_{n}=a_{n-1}-3[/tex] , [tex]n\geq 2[/tex]
check:
when n = 2
[tex]a_{2}= a_{1}-3[/tex]
[tex]a_{2}=18-3 = 15[/tex]
