Answer
The sequence is arithmetic.
The common difference: $d=2.5$
The general term: $a_{n}=2.5n-6.5$
Work Step by Step
$a_{2}-a_{1}=-1.5-(-4)=2.5$
$a_{3}-a_{2}=1-(-1.5)=2.5$
$a_{4}-a_{3}=3.5-1=2.5$
$a_{5}-a_{4}=6-3.5=2.5$
$a_{6}-a_{5}=8.5-6=2.5$
As the difference between each term and the preceding term is the same, the sequence is arithmetic.
The general term is
$a_{n}=a_{1}+(n-1)d$
where $d$ is the common difference.
$a_{1}=-4$, $d=2.5$
$\implies a_{n}=-4+(n-1)(2.5)$
Or $a_{n}=-4+2.5n-2.5=2.5n-6.5$
