Answer
$0$
Work Step by Step
The formula for finding the arithmetic mean is $\dfrac{x+y}{2}$.
Arithmetic mean is the middle term of any $3$ consecutive terms of an arithmetic sequence.
In this sequence the consecutive numbers are $a_{n-1}$, $a_{n}$, $a_{n+1}$ so the formula for arithmetic mean is: $$a_{n}=\dfrac{a_{n-1} + a_{n+1}}{2}$$
Substitute the given values in the formula:
$a_{n}$=$\dfrac{-2x+2x}{2}$
$a_{n}=0$
