You need to sub your X and Y values in. Take (-1,-3) for example: if you sub in these values, your equation y=-2x -1 will become (-3)=-2(-1) - 1. However, if you simplify it out, you'll realise that it doesn't make sense as you'll get -3=-1 which is clearly untrue, thus (-1,-3) is the only pair that doesn't satisfy your function.
