Answer:
3 , 11, 25, 45
Diff 8 14 20
Diff 6 6
The second differences are the same. The sequence is quadratic and will contain an n^2 term. The coefficient of n^2 is always half of the second difference. In this example, the second difference is 6. Half of 6 is 3 so the coefficient of n^2 is 3
therefore 3n^2
3 11 25 45
3n^2 3 12 27 48
Remainder 0 -1 -2 -3
Difference -1 -1 -1
linear sequence with nth term -n+1
so nth term of quadratic sequence in 3n^2-n+1
