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# Binomial Expansion Question C2 Watch

1. The bit underlined in red. What is going on?
2. (Original post by scientific222)
The bit underlined in red. What is going on?
Not sure what you do not understand

(n-2)! = (n-2) x (n-3)!

Since (n-2)! = (n-2)(n-3)(n-4)(n-5) ... ... ... ...

And (n-3)! = (n-3)(n-4)(n-5) ... ... ... ...
3. (Original post by TenOfThem)
Not sure what you do not understand

(n-2)! = (n-2) x (n-3)!

Since (n-2)! = (n-2)(n-3)(n-4)(n-5) ... ... ... ...

And (n-3)! = (n-3)(n-4)(n-5) ... ... ... ...
I understand now thank you. I previously didn't understand the use of variables in factorials , it was the first time I came across it
4. (Original post by scientific222)
I previously didn't understand the use of variables in factorials , it was the first time I came across it
Ah .. ok

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