n n\,n and k k\,k are integers. Prove algebraically that the sum of n(n+2k)n(n + 2k)n(n+2k) and k2 k^2\,k2 is always a square number. Give the square number in terms of n n\,n and kkk.
207 exam-style questions on OCR GCSE Maths Proof. Each one has a worked solution and a mark scheme showing where the marks go.