Prove that (2n+3)2−(2n−3)2(2n + 3)^2 - (2n - 3)^2(2n+3)2−(2n−3)2 is always a multiple of 12, for all positive integer values of nnn.
14 exam-style questions on CIE IGCSE Maths Proof. Each one has a worked solution and a mark scheme showing where the marks go.