Answer
The sequence is arithmetic.
Common difference $d=2.35$.
Work Step by Step
We compute the difference between each term and the preceding term. If the difference is same, then the sequence is arithmetic.
$a_{2}-a_{1}=-4.3-(-6.65)=2.35$
$a_{3}-a_{2}=-1.95-(-4.3)=2.35$
$a_{4}-a_{3}=0.4-(-1.95)=2.35$
$a_{5}-a_{4}=2.75-0.4=2.35$
$a_{6}-a_{5}=5.1-2.75=2.35$
The common difference $d=2.35$ is constant and therefore the sequence is arithmetic.