Answer
common difference = $-2$
The first four terms are: $4, 2, 0, -2$
Work Step by Step
To find the first four terms, substitute $1, 2, 3, 4$ for $n$ in the given formula.
$c_1 = 6-2(1) = 6-2= 4$
$c_2= 6-2(2) =6-4=2$
$c_3 = 6-2(3)=6-6=0$
$c_4 = 6-2(4) = 6-8 = -2$
The terms decrease by $2$ units, so the sequence is arithmetic with a common difference of $-2$.
