掌握了一元函数微分学之后,便可以进一步学习多元函数微分学。由于函数的自变量个数增多,引起了一系列的变化,使多元函数与一元函数在若干方面存在本貭的差异。虽然如此,处理多元函数問題时,在相当程度上,于一定条件下可借用一元函数的有关概念与方法。所以,随时注意这种区别和联系,对掌握多元函数微分学会有一定的帮助。上述的区别和联系,当从一元函数过渡到二元函数的研究吋,便充分得到显示;至于从二元推广到多元,則仅需在技巧方面下工夫,而沒有原則上的困难。因此,本文重点討論二元函数,其結果不难推广到多元函数。由于篇幅有限,仅討論最基本的概念:极限,連續,微商与微分,并涉及一些初步应用。学过一元函数微分学的讀者都可以看懂。进一步的材料可参考[1],[2],[3],[4],[5]各书。 Once you have mastered the one-variable function calculus, you can learn more about differential function differential calculus. As the number of independent variables of the function increases, a series of changes are caused, making the difference between the multivariate function and the one-variable function in several aspects. However, when dealing with the problem of multivariate functions, to a certain extent, the relevant concepts and methods of one-variable functions can be borrowed under certain conditions. Therefore, always pay attention to this difference and contact and have some help in mastering the differential function of multivariate functions. The above differences and connections are fully demonstrated when the transition from a one-element function to a binary function is studied. As for the promotion from binary to multivariate, it only requires skill in terms of skills, and there is no difficulty in principle. Therefore, this article focuses on the binary function, and the result is not difficult to generalize to a multivariate function. Due to limited space, only the most basic concepts are discussed: limit, continuous, derivative and differential, and some preliminary applications are involved. Readers who have studied the one-dimensional function calculus can read it. For further materials, refer to [1], [2], [3], [4], [5] books.