Answer
A.P. with common difference $-5$ and initial term $8$.
Work Step by Step
Since,we have $8,3,-2,-7,-12....$
$a_2-a_1=3-8=-5$;
$a_3-a_2=-2-3=-5$;
$a_4-a_3=-7-(-2)=-5$
and
$a_5-a_4=-12-(-7)=-5$
Hence, we can conclude that this is an A.P. with common difference $-5$ and initial term $8$.
