Răspuns:
Explicație pas cu pas:
1) 3*2/(1*2) +1*2*3 = 3 +6 = 9
2) 1 + 1 = 2
3) n(n-1)/(1*2) = 28
n(n-1) = 2*28 = 56 = 7*8
Se vede ca n =8
4) C(5;2) = 5*4/(1*2) = 10
5) A(6;2) = 6!/(6-2)! = 6!/4! = 6*5*4*3*2*1/(4*3*2*1) =6*5 =30
C(6;4) = 6!/(4!)(6-4)! = 6*5*4*3*2*1/(4*3*2*1)(2*1)) = 3*5 = 15
30 -2*15 = 0
6) C(4;2) = 4*3/(1*2) = 6
7) n + n = 10, 2n = 10, n = 5
8) (n-3)(n-4)(n-5)!/((n-5)! = 6
(n-3)(n-4) =6 = 3*2
Se vede ca n = 6
