The first volume of calculus is nothing more than limit, differential and integral. First of all, we must understand the concept of limit. Differential is the limit of the ratio of infinitesimal change of function value to infinitesimal change of variable, which reflects the problem of change rate, so derivative value can reflect the growth of function. Integral is the limit of summation under function after infinite division of variables. The latter two are essentially limits, and LZ must understand the relationship between the three, so that the topic can be done well.