Răspuns:
a) n ∈ {5; 6; 7; 8; 9; 10; 11}; b) n ∈ {1; 2; 3}
Explicație pas cu pas:
a)
[tex]\frac{^{4)} 1}{3} < \frac{n}{12} < \frac{^{4)}3}{3} \\ 4 < n < 12[/tex]
=> n ∈ {5; 6; 7; 8; 9; 10; 11}
b)
[tex]\frac{1}{9} < \frac{1}{2n + 1} < 1 \\ 1 < 2n + 1 < 9 \: \: |_{(- 1)} \\ 0 < 2n < 8 \: \: |_{( :2 )} \\ 0 < n < 4[/tex]
=> n ∈ {1; 2; 3}
