SOLUTION: Construct a difference table to predict the next term of the sequence -1,4,21,53,103,174,269,...

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Question 1151348: Construct a difference table to predict the next term of the sequence
-1,4,21,53,103,174,269,...

Answer by greenestamps(13203) About Me  (Show Source):
You can put this solution on YOUR website!


A table showing the original sequence and the rows of first, second, and third differences:
-1    4   21   53  103  174  269
    5   17   32  50   71   95
      12   15  18   21   24
         3    3   3    3

There is a constant difference of 3 in the row of third differences. To find the next term in the sequence, place another difference of 3 in the third row and work back up the array:
-1    4   21   53  103  174  269   391
    5   17   32  50   71   95   122
      12   15  18   21   24   27
         3    3   3    3    3

The predicted next term of the sequence is 391.

By the way.... The constant difference in the row of third differences means the sequence is generated by a polynomial of degree 3. The coefficient of the leading term is the constant difference (3) divided by the factorial of the degree of the polynomial (3!=6). So the coefficient of the leading term is

%283%2F%283%21%29%29+=+3%2F6+=+%281%2F2%29

and the leading term of the polynomial is then

%281%2F2%29x%5E3