The problem of accuracy means that when calculating the limit, if the equivalent infinitesimal substitution is carried out, the infinitesimal order will be involved, and if the infinitesimal order is not enough, it may lead to calculation errors.

1) The accuracy problem mainly occurs in the calculation of the fractional limit: if the numerator contains addition and subtraction operations, the order of infinitesimal must reach the order of denominator when the numerator is equivalently replaced, and the same is true when the denominator is equivalently replaced.

2) For limit calculation problems that are not fractions, if addition and subtraction operations are involved, the accuracy (order) of addition and subtraction items should be consistent when they are replaced by equivalents.

Limit of mathematical equivalent infinitesimal precision problem;

Basic concepts of mathematical analysis. It refers to such a changing trend and the trend value (limit value) that the variable gradually tends to be stable in a certain changing process.

Limit method is the basic method to study functions in mathematical analysis. All the basic concepts of analysis (continuous, differential, integral and series) are based on the concept of limit, and then all the theories, calculations and applications of analysis can be realized. Therefore, it is very necessary to define the concept of limit accurately, which is a fundamental problem related to the reliability of theory and calculation analysis.