|Xn-a| is used to prove that the limit of the sequence Xn is a and the limit is a, which means that a number can be found.
Generally speaking, as long as the absolute value of the difference between each item and A is less than the given value of the item (N+ 1), it is recorded as n.
Any small number, generally called ε.
2. Since ε can be arbitrarily small, it implies that an item can always be found, and this item is the nth item. From the back of this article,
The smaller the difference with a, the better, which proves that a is the limit of sequence.
This proves that most college students can't understand its ideological essence all their lives, and they are all big dishes.
(probably) In order to prove convenience, we often zoom in and out, which is not approximate.
But it is stricter and more accurate, which many people don't realize, but misunderstand.
4. It is more strict and convenient to zoom in and out, so if | xn-a |
The n is more in line with the limit requirements. This is because the newly discovered n, every term after n is not less than ε, but
Less than ε/2. This is a reduction method, not an amplification method, which means: smaller than the small one, smaller than the original one!
5, review calculus:
A, the concept is clear, and the concept is summarized again;
B, independently derive the main formulas and summarize the methods;
C, solve the problem, solve at least thousands of problems, and then summarize the types of problems.
D, you'd better find some junior students to tutor you, and then you will be an expert!
(mentality during counseling: there is no unclear concept; There is no problem that cannot be solved; Every teacher can't pass )