一、基本概念 1.数列的极限,是当项数n无限增大时,数列的项a_n无限趋近于常数A,记作(?) a_n=A,即当n→∞时,a_n→A_o而函数的极限有两种情况:(?)f(x)=A,(?)(x)=A_o要注意x→∞包括x→+∞和x→-∞,x→x_o包括x→x_o~+和x→x_o(?) 2.函数f(x)在点x=x_o处连续必须具备以下三个条件,缺一不可:①f(x)在点x_o的某一邻域内有定义;②(?)(x)存在;③f(x)在点x_o处的极限等于f(x)在点x_o的函数值, First, the basic concepts 1. The limit of the series, is when the number of items n increases indefinitely, the series of items a_n infinitely close to the constant A, recorded as (?) a_n = A, that when n → ∞, a_n → A_o The limit of the function has two cases: (?)f(x)=A,(?)(x)=A_o Note that x→∞ includes x→+∞ and x→-∞, and x→x_o includes x→x_o ~+ and x→x_o(?) 2. The function f(x) must have the following three conditions consecutively at the point x=x_o, which are indispensable: 1f(x) is defined in a neighborhood of point x_o; 2 (?)(x) exists; the limit of 3f(x) at point x_o is equal to the function value of f(x) at point x_o,