Add Maths 4037: Five Mistakes That Cost the Most Marks (and How to Fix Them)
By Zaheer | Updated 14 October 2026 Disclosure: I created the Add Maths Companion app mentioned at the end and sell it on Gumroad. Everything in this post is free to use without it. This is independent study material, not affiliated with Cambridge or any exam board. Most marks lost in O Level Additional Mathematics (4037) are not lost on hard ideas. They are lost on small, repeatable slips, such as forgetting to reject an impossible answer or solving a trig equation in the wrong range. Here are five of the most common ones. For each, you will see the wrong working, the right working, and a quick way to avoid it. Mistake 1: Keeping an answer the logarithm can't accept Question: Solve log 2 x + log 2 (x − 2) = 3. The slip: solving the quadratic correctly, then giving both roots as the answer. Right working: Combine the logs: log 2 [x(x − 2)] = 3 Convert: x(x − 2) = 2 3 = 8 Rearrange: x 2 − 2x − 8 = 0, so (x − 4)(x + 2) = 0, giving x = 4 or x = −2 ...