Anonymous

Sure. The common difference gives you the recursive part: a_(n+1) = a_n + d . . . . . [using _ to indicate a subscript] ...and the known value of a_5 gives you a fixed reference point.

Anonymous

Let b = common difference of an arithmetic sequence. Than: a(n) = a(n - 1) + b where n > 1 and a(1) is whatever your first term is (which is your stop-case in the recursion).

Anonymous

yes. you can subtract the difference from the 5th term 4 times to get the first term. you know the difference, that's all you need.