First of all, it is worthy of recognition that your thinking is divergent, which is a manifestation of mastering what you have learned. As for the existing problems, I think you have done too little practice. I suggest doing more similar questions. In fact, there are only a few kinds of math problems, and the changes are not great. You only need to master a few standard questions's solutions, which are very practical. After doing such a problem, the idea will soon be in place, and the rest will be much simpler.

The main reason for miscalculating this problem is that you are too careless in doing it and your temper slowly wears off. You must not be anxious. Just pay more attention at ordinary times. When you pick up the pen, always remind yourself to be careful and not impatient. When this idea becomes a habit, you basically overcome this problem. Of course, if it is a technical mistake, then you should read more books, and mastering textbook knowledge is king.