Mathematics for IGCSE & O level - Sequences (Section 2 - No. 32)
Which of these is a quadratic sequence?
5, 10, 15, 20,...
1, 4, 9, 16, ...
2, 6, 18, 54, ...
3, 6, 9, 12, ...
Explanation
A quadratic sequence is identified by a constant second difference.