Question

Combinations question help!

Answer 1

\[\left(\begin{matrix}n \\ 6\end{matrix}\right) = \left(\begin{matrix}n \\ 4\end{matrix}\right)\] Find value for n. errrrr :(

Answer 2

n!/(n-6)!6! = n!/(n-4)!4!
1/(n-6)!4!=1/(n-4)!4!
(n-4)!4!=(n-6)!6!
(n-4)!4.3.2.1 = (n-6)(n-5)(n-4)!.6.5.4.3.2.1
1=(n-6)(n-5).6.5
30(n-6)(n-5)-1=0
solve for n, now, just remember that n > 0

Answer 3

n = 10 u know
10C6=10C4

Answer 4

@extremity , i dont understand the second step LHS changing from 6! to 4! and also the 4th step RHS... @powerrangers69, how did you do that?

Answer 5

nCk = nCn-k
nCk = n!/k!(n-k)!
nCn-k = n!/(n-(n-k)!k!

Answer 6

A useful identity to remember is
nCr = nC(n-r)
Example:
100C23 = 100C(100-23) = 100C77
For a proof, see powerangers69's explanation.