In an arithmetic sequence, the next term is found by adding a constant term to each number to arrive at the next number. The common difference can be found by subtracting the first term from the second term.
-8.6, -5.0, -1.4, 2.2, 5.8....the common difference here is 3.6 -8.6 + 3.6 = -5.0 -5.0 + 3.6 = -1.4 1.4 + 3.6 = 2.2 2.2 + 3.6 = 5.8 so this IS an arithmetic sequence.
2,-2.2, 2.42, -2.662, 2.9282...there is no common difference..so this is not an arithmetic sequence
5,1,-3,-7,-11....common difference is -4 5 + (-4) = 1 1 + (-4) = -3 -3 + (-4) = -7 -7 + (-4) = -11 this IS an arithmetic sequence
-3,3,9,15,21...common difference is 6 -3 + 6 = 3 3 + 6 = 9 9 + 6 = 15 15 + 6 = 21 this IS an arithmetic sequence
-6.2, -3.1, -1.55, -0.775, -0.3875...this is not an arithmetic sequence
