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)