difficult question I need help with.
We are asked to show that $n! = \sum_{k=0}^n (-1)^k\binom{n}{k}(n-k)^n$
There is also a hint "try to think of the number of permutations of n elements using inclusion-exclusion"
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3http://math.stackexchange.com/questions/591350/difference-of-powers/594462 – lab bhattacharjee Dec 09 '13 at 16:31