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
(not sure about the first two questions cause the question is kinda confusing. just know that the inequality in the question represents "x is less than or equal to 6")