Question

http://prntscr.com/9hy8d5

Answer 1

Are these correct?

Answer 2

@Rushwr

Answer 3

haha thats ok cx

Answer 4

i dont know this either o-o
Maybe @Owlcoffee knows ?

Answer 5

@inkyvoyd

Answer 6

Those are correct

Answer 7

Permutations and combinarions are the amount of pairs we can choose on a given amount of data.
There are two major permutations and combinations to take into consideration:

Combinations with repetition:
We can define this as the combinations of all the given elements including their repetition, this means every single one of the element will have the same number of combinations as there are alements (of course, since it can be repeated).
So we will arrive to the formula for permutations WITH repetition "Pr": \[P_r= n^r\]
Where "n" is the amount of elements and "r" the amount of pairs.

Combinations without repetition:
This one is a little more complicated, because we are not allowed to actually repeat our combinations, for example, on a code that being "4-4-4-4".
Now, note something interesting about this, we will ONLY lose the first combination by any given element with itself, and this'll make it into a permutation that is increasing, and there we define the function of "factorial".
By this logic we arrive into the formula of permutations without repetition "Pw":
\[P_w=\frac{ n! }{ (n-r)! }\]
Where again, "n" is the number of elements and "r" the number of combinations desired.

Answer 8

k ty