Question

Find the nth term of this quadratic sequence -1,8,23,44,71,104

Answer 1

difference between each term :_

9 15 21 27 33
second difference:-
6 6 6 6
Dividing this by 2 = 3
so first part of nth term is 3n^2
Substituting n into 3n^2 :-
= 3 12 27 48 75
Now take these values from the original numbers:-
-4 -4 -4 -4 -4

So the required nth term is 3n^2 - 4