Permutation & Combinations Flashcards
1
Q
nPn =
A
n!
2
Q
nPr =
A
n!/(n-r)!
= nCr x r!
3
Q
nCr =
A
n!/(n-r)!r!
4
Q
If r>n/2, nCr
A
nC(n-r)
5
Q
nC(r-1) + nCr =
A
(n+1)Cr
6
Q
(a+b)^n =
A
nC0 a^n + nC1 a^(n-1)b + nC2 a^(n-2)b^2 + …
7
Q
nCr . a^(n-r).b^r =
A
n!/(n-r)!r! a^(n-r).b^r
