Binomial coefficient expansion question

Question

I'm trying to follow this expansion (linked below) for one of my classes, but nothing I have tried is proving successful.

Any hints or help would be very appreciated.

Thanks :)

Binomial coefficient expansion

I tried to edit this to include a cordial greeting, but it isn't working. Apologies for sounding abrasive. — cthodrums, Jun 22 '20 at 08:40

score 0 · Accepted Answer · answered Jun 22 '20 at 08:45

0

There is a mistake, here is the correct expansion $${n\choose r}=\frac{n!}{r!(n-r)!}=\frac{n}{n-r}\cdot\frac{(n-1)!}{r!(n-1-r)!}=\frac{n}{n-r}{n-1\choose r}$$

answered Jun 22 '20 at 08:45

Maryam

1,889

Thank you so much @Maryam. I was really confused over whether I was missing something very elementary. – cthodrums Jun 22 '20 at 10:15

Binomial coefficient expansion question

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