Alex says the common difference for an arithmetic sequence is always negative because of the definition of "difference." Why is he wrong? Write an arithmetic sequence to show he is wrong. The common difference is the constant change between consecutive terms in an arithmetic sequence, so it must be positive. wrong since its common difference, , is not negative. The arithmetic sequence 2, 4, 6, 8,... shows that Alex is must be either positive or negative. could be any value. must be positive.