1. The problem statement, all variables and given/known data Hello, This expression was derived from a polygon word problem and I need to find a closed form for it with repeated substitution (I think). T(k, n) = T(k, n-1) + (k-2)(n-1) + 1 2. Relevant equations 3. The attempt at a solution Get a pattern like: = T(k, n-2) + (k - 2)(2n - 3) - 2 subs. = T(k, n-3) + (k - 2)(3n - 6) - 3 subs. = T(k, n-4) + (k - 2)(4n - 10) -4 subs. . . . I'm not sure how to express the 1, 3, 6, 10 sequence in terms of number of substitutions.