FAC.txt

Permutations - 

factorial is number of possibilities

e.g.
how many words can be made by rearranging the letters of VECTOR

6! = 6x5x4x3x2x1 = 720

trickier permutations-
how many 4 letter words can be made by rearranging GHIJKLM

7!/3! = 840

options!/(options-limit)!

because 7!/3! = 7x6x5x4 x 3!/ 3!

Combinations
if you dont care about order e.g abb is the same as bab then divide by the factorial of the limit 
e.g.

7!/(7-4)!4!

if we have n objects and want to choose a group of r of them where order does not matter,
(n)
(r)     = n!/r!(n-r)!


82!/80!2!

82 * 81 / 2!


Binomial Theorem

fancy way to multiple out brackets ig

(a+b)^n = n sigma r=0 (n)a^(n-r)b^r
		      (r)



f'(1) = 6

6*e^(6-b)