Answer
a. $-10,10,30,50,70$
b. $20$
c. see below
.
Work Step by Step
a.
$a_{1}=-10+20(1-1)=-10$,
$a_{2}=-10+20(2-1)=10$,
$a_{3}=-10+20(3-1)=30$,
$a_{4}=-10+20(4-1)=50$,
$a_{5}=-10+20(5-1)=70$
(b)
$10-(-10)=30-10=50-30=70-50=20$
The common difference is $20$.
(c) graphed using desmos.com