There are addition and subtraction rules for limits, but the premise is that both addition and subtraction limits must exist. Taking this problem as an example, ln( 1+x) in the whole limit is divided into two formulas LIM (LNX/( 1+x) 2-LNX) and lim ln( 1+x). Obviously, the limit of the second formula exists and the limit of the first formula is derived, so it is feasible to divide it into two formulas. However, it is usually not feasible to decompose the limit operation into addition and subtraction, which requires specific analysis. Grasp a principle, once the limit formula is separated, don't add it together, it must be wrong!