This kind of mistake is due to carelessness. If we want to say how to improve it, we can only be more careful when doing the questions. But if it doesn't matter how carefully you think, I think you might as well get into the good habit of checking after answering questions.

There are also two situations when checking. If you have enough time, go over the previous problem-solving ideas for the first time and check them. The second time, you should check it from the perspective of calculation (this is to avoid the inertia thinking of solving problems directly leading to calculation errors or inertia in review).

If there is not enough time, you can choose the way to view it.