MF55: Binomial coefficients and related functions

[jarvisob]

Hi nice video. I'm wondering why doesn't 7 factorial get multiplied like the m factorial above i.e. 1x2x3...x7. Instead you only multiply it from 4 onwards. 4x5x6x7. Cheers

[njwildberger]

Hi jarvisob,

The 7 in the example is playing the role of (m+k), where m and k are 4 and 3. We multiplied the answer 7x6x5x4 / 4x3x2x1 on the top and bottom by 3x2x1.

[peterhi503]

Wildberger, excellent video, as always. Note that P4,3 is the fifth row, fourth column.

[njwildberger]

Hi peterhi503

Thanks. The way I am counting rows and columns here is to start with 0. That way P4,3 really is in the 4th row, 3rd column.