Find the arithmetic mean a Subscript n of the given terms.

a Subscript n minus 1equals5​, a Subscript n plus 1equalsminus2

To find the arithmetic mean of a Subscript n in this scenario, we need to calculate the average of a Subscript n minus 1 and a Subscript n plus 1.

arithmetic mean a Subscript n = (a Subscript n minus 1 + a Subscript n plus 1) / 2
arithmetic mean a Subscript n = (5 + (-2)) / 2
arithmetic mean a Subscript n = 3 / 2
arithmetic mean a Subscript n = 1.5

Therefore, the arithmetic mean of a Subscript n is 1.5.