Math homework question?! ***10 points?!?

If there are grid coordinates that are (2,-1) (4,3) and (0,5) and you follow this rule which is (x,y) ----> (-x,-y) what would (2,-1) change to. I know (4,3) would change to (-4,-3) and (0,5) would change to (0,-5) but what would (2,-1) change to. And the answer is not (-2,-1) because I tried that already and my teacher marked it wrong. Did he make a mistake correcting the question? If not, what is the answer? Thank you so much to everyone who helps! And you don't need to give me the answer, I am just asking for help with the question. Thank you all so much!