8≤ 2n+6< 16 | -6
2≤ 2n< 10 | :2
1≤ n<5
deci n∈ [1,5)
=>B= [1,5) interectat cu N= {1,2,3,4}
Submult lui B sunt
Ф, {1},{2},{3},{4},{1,2},{1,3},{1,4},{2,3},{2,4},{3,4},{1,2,3},{1,2,4},{1,3,4},{2,3,4},{1,2,3,4) sunt in numar de 2⁴=16, deci n-am pierdut niciuna
O seara buna!