Tell if each of the following is an arithmetic sequence. find the common difference if it is Arithmetic.
1). 3, 7, 11, 15, 19, ... ____________
2). 4, 16, 64, 56, ... ____________
3). 48, 24, 12, 6, 3, ... ___________
4). 1, 0, -1, -2, -3, .... _____________
5). 9.5, 7.5, 5.5, 3.5, ... ___________