Proof steps:

1. Verify that n=n0 holds (n0 is the initial value of n).

2. Assuming that the original proposition holds when n = k, it is proved that n = k+ 1 also holds.

3. It is concluded that the original example holds for all natural numbers with n≥n0.

Matters needing attention in the certificate:

1 and n=n0 must be verified. This step is called inductive basis (equivalent to knocking down the first domino).

2. The key step is to assume that the original proposition holds when n = k, and then prove that n = k+ 1 also holds. This step is called inductive hypothesis (the function is to prove that there is such a law between any two adjacent dominoes: the first one falls, and the last one must fall), and this step is also the most difficult.

3. In the process of proving that n = k+ 1 is also true, we must use the hypothetical conclusion.

4. In the process of proving that n = k+ 1 is also true, we should pay attention to two points: first, find the form of hypothesis, so as to use the conclusion of hypothesis, and then find the form of proof result.

5, when n = k+ 1, we should pay full attention to the difference with n = k, increase or decrease.