【摘要】In this paper, leads to Fermat's theorem Rolle Mean Value Theorem, and then constructing auxiliary function of the Lagrange mean value theorem and Cauchy's Mean Value Theorem to prove that. The use of Differential Mean Value Theorem (Rolle theorem, Lagrange's theorem, Cauchy's theorem) to solve a number of derivative and limit the problem. Through the polynomial approximation to function, resulting in more than a Peano-type and Lagrange remainder of the Taylor formula, using elementary functions Maclaurin expansions to address the limits and the approximate evaluation of the problem. Through the study of this article requires proficiency in differential intermediate value theorem and Taylor's formula to prove, using theorem to solve a number of conclusions related questions, so can a clear understanding of this kind of problem solving ideas.【关键词】Differential intermediate value theorem Taylor formula Derivative More than最后一个我不怎么会,所以。。。。别介意哦