Answer:
The sequence is arithmetic
Step-by-step explanation:
we know that
In an arithmetic sequence, the difference between consecutive terms is always the same and is called common difference
In this problem we have
[tex]3,9,15,21,...[/tex]
Let
[tex]a1=3, a2=9,a3=15,a4=21[/tex]
[tex]a4-a3=21-15=6[/tex]
[tex]a3-a2=15-9=6[/tex]
[tex]a2-a1=9-3=6[/tex]
The sequence is arithmetic
The common difference is equal to [tex]6[/tex]
