So say your showing your math workings for simplifying your answer.

It may have multiple terms of a denominator of x. Should you declare x != 0 on every step of your simplification process. Or only write it on your final result? What is considered the best practice ? I currently write it on every step of my calculations just to avoid losing a mark (i have no idea how the examiner might feel about it). So i play it safe.

But in general - what is a the common practice?