29/09/2026
Dividing both sides of x² = 9x by x gives x = 9 – and accidentally throws away x = 0. Better: move everything to one side, factorise: x² − 9x = 0 → x(x − 9) = 0, so x = 0 or x = 9. The rule is: don’t divide by something that could be zero – factorise instead. If your child is heading for Higher tier, this is exactly the kind of detail that gains extra marks. DM me “QUADRATIC” for more practice questions.