โจทย์combinatoricครับ
ช่วยหน่อยนะครับ
1.Determine the number of ways to choose five numbers from the first eighteen positive intergers such that any two chosen numbers differ by at least 2.
2.Let n be an odd interger greater than 1.Find the number of permutation p of the set{1,2,...,n} for which
2[/p(1)-1/+/p(2)-2/+.../p(n)-n/]=(n.n)-1
|