Ah well, I guess spock1 will just have to take his pick. For me the difference between 2 and -4 is not 6 but -6 and in maths textbooks the difference between the two would be made clear.
Waugh2 is correct. The constant difference is 6 not -6. The absolute difference between 2 and -4 is 6, but to get from 2 to -4 needs the addition of -6. Constant differences are always added.
Ok, I just looked up 'constant difference', and it did state that they are always added. Then it went on with some examples of arithmetical sequences; however, they were all positive We all know that you can add negative numbers, so what is the correct answer?............I must admit at this point I don't know.
Since "difference" implies subtraction the question is somewhat ambiguous, IMO. In such cases I would resign myself to the traditionally accepted definition as stated above and go with the addition of six to each resulting term.
Hmmm . . . I don�t suppose phrasing the question as �constant change� would help none?