等价量代换在和式极限中的应用

Limit is the soul of differential calculus, limits’ calculation is an important content of the limit theory. For how to calculate the limits added, in many mathematics textbooks are researched , However, there are few specialized contents to study them. A few common solutions on limits added were explained in some references，in this paper，several simple new solutions on limits added will be introduced by giving several important theorems。