If we begin with the first term, 2, mult. it by 4 and then subtract 3, we get 5 (not 4, as shown).
If we begin with 4, mult. it by 4 and then subtract 3, we get 13. This agrees with the terms of the given sequence.
If we begin with 13, mult. it by 4 and then subtract 3, we get 49. This agrees with the terms of the given sequence.
Remove the first term, 2, and then the remaining terms follow the given procedure for finding terms.
First compute the perimeter of the pool:
(21+33)*2=108 foot.
Since the material cover 232 ft^2, then it is sufficient to divide the above number over the length of the border like this:
232/108=2.1
The trip can be 2.1 ft in wide.