k k\,k is an integer. Prove algebraically that the expression (k−1)(k−2)+k−1(k - 1)(k - 2) + k - 1(k−1)(k−2)+k−1 is always a square number.
Practise OCR GCSE Maths Proof with exam-style questions for Foundation and Higher tier. 56 questions, matched to the OCR GCSE Maths (J560) specification and written in the written papers style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.