Answer
a. $-6.-10.-14.-18.-22$
b. $-4$
c. see below
Work Step by Step
a.
$a_{1}=-6-4(1-1)=-6$
$a_{2}=-6-4(2-1)=-10$
$a_{3}=-6-4(3-1)=-14$
$a_{4}=-6-4(4-1)=-18$
$a_{5}=-6-4(5-1)=-22$
(b)
$-10-(-6)=(-14)-(-10)=-18-(-14)=-22-(-18)=-4$
The common difference is $-4$.
(c) graphed using desmos.com