Answer
common difference = 2
The first four terms are: $-3, -1, 1, 3$
Work Step by Step
To find the first four terms, substitute $1, 2, 3, 4$ for $n$ in the given formula.
$a_1 = 2(1)-5 = 2-5=-3$
$a_2=2(2)-5=4-5=-1$
$a_3 = 2(3) - 5 = 6-5 = 1$
$a_4 = 2(4) - 5 = 8 - 5 = 3$
The terms increase by $2$ units, so the sequence is arithmetic with a common difference of $2$.
