Sometimes a mathematical formula is too long to be written on one line and must be written on the next line. This is called the "broken line" of mathematical formula.
Regarding folding, there are some precautions:
The general practice is to naturally enter the next line without splitting the numbers (for example, if a four-digit 1234 is broken, it will become two ten-digit 12 and 34. ) so it is usually a line break after the operator.
Because a line break follows an operator, some people are willing to let the operator at the end of the line that starts after the line break begin (that is, if the line break follows the+sign, the new line starts with the+sign).
In addition, in order to make the folding more intuitive, sometimes people are willing to indent slightly from the next line to indicate that this is an unfinished continuation of the previous line. If you want to continue multiple lines and align the indented lines, continue this method until the beginning of the new line returns to the alignment of the first line.
Another thing to pay attention to is to avoid endless line breaks. Once a long formula appears, it must be broken in order to maintain its integrity. At this time, start a new line from the next equal sign (that is, don't indent). This format is easy for people and themselves to read and find.