Here are the first 5 terms of a quadratic sequence.
6 12 20 30 42
Show that the n n\,nth term is n2+3n+2n^2 + 3n + 2n2+3n+2 and hence determine whether 156 is a term in the sequence.
201 exam-style questions on OCR GCSE Maths The Nth Term of a Quadratic Sequence. Each one has a worked solution and a mark scheme showing where the marks go.