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
\(3,9,15,21,...\)
Let
\(a1=3, a2=9,a3=15,a4=21\)
\(a4-a3=21-15=6\)
\(a3-a2=15-9=6\)
\(a2-a1=9-3=6\)
The sequence is arithmetic
The common difference is equal to \(6\)
