What does it mean to give reasons for your answer in maths?

Answer 1

It means that, instead of just giving an answer (which, of course, may be right or wrong), you explain how you obtained it - either in general outline, or perhaps more detailed, explaining every step.

Answer 2

In mathematics, giving reasons for your answer means providing logical and mathematical justifications for your solution or conclusion. This may involve explaining the steps taken to arrive at the answer, referencing relevant theorems or principles, and demonstrating the correctness or validity of your reasoning. Giving clear and coherent explanations helps to ensure understanding, accuracy, and effective problem-solving in mathematics.