Very simple, first understand the meaning of absolute value, absolute value is the distance from a point on the number axis to the origin. Remember, this is a positive distance. Since it is a positive number, and this topic has only two absolute values, then X can be discussed in sections. The topic requires that X can take all numbers, so we divide X into three sections. When x

In the future, when you encounter such a problem with absolute value, the first thing to do is to remove the absolute value and then use the number axis. Remember that neither of these two questions is a problem (except for the competition). Usually two or three absolute values are the most, which can be discussed in different situations. I hope you have a good grasp.