This exam mainly examines the application of binomial theorem and mathematical induction.

(1) Remember,

rule

(2) If the original extension becomes:

rule

therefore

Then sum and prove it by mathematical induction.

Solution: (1) Note,

Then (4 points)

(2) If the original extension becomes:

rule

So (6 points)

When, the conclusion is established.

Assumption holds, that is to say

At that time,

The conclusion is valid. (9 points)

So when ... (10)