1. Let's consider the set A = {a,b,c,d,e} the different combinations with
repetition of these five elements are:
a) Combinations with repetition of 5 taken elements in ones: a, b, c, d, and e
b) Combinations with repetition of 5 taken elements in twos:
As before ab ac ad, ae bc bd be cd ce and de but now also the groups
with repeated elements: a2 bb, cc dd, and ee.
c) Combinations with repetition of 5 taken elements in threes
As before abe abc abd acdace, ade bed, bee bdeand ode but now
also the groups with repeated elements: aab, aac aad aae bba bbc
bbd bbe cca och. ccd cce dda ddb, ddc dde aaa bbb occ ddd and
eee​