Explicație pas cu pas:
A = {x ∈ N* | x ≤ 4}
=> A = {1; 2; 3; 4}
B = {x ∈ N | x = 2a - 1, a ∈ A}
a = 1 => x = 2×1 - 1 = 2 - 1 = 1
a = 2 => x = 2×2 - 1 = 4 - 1 = 3
a = 3 => x = 2×3 - 1 = 6 - 1 = 5
a = 4 => x = 2×4 - 1 = 8 - 1 = 7
=> B = {1; 3; 5; 7}
C = {y ∈ N | y = 2x + 1, x ∈ B}
x = 1 => y = 2×1 + 1 = 2 + 1 = 3
x = 3 => y = 2×3 + 1 = 6 + 1 = 7
x = 5 => y = 2×5 + 1 = 10 + 1 = 11
x = 7 => y = 2×7 + 1 = 14 + 1 = 15
=> C = {3; 7; 11; 15}
(A∩B) ∪ (B∩C) = {1;3} ∪ {3;7} = {1; 3; 7}
(A - B) ∪ (B - C) = {2;4} ∪ {1;5} = {1; 2; 4; 5}
(A - B) ∩ (B∩C) = {2;4} ∩ {3;7} = {Ø}
(B∩C) ∪ A = {3;7} ∪ {1;2;3;4} = {1; 2; 3; 4; 7}
(A∪B) ∩ C = {1;2;3;4;5;7} ∩ {3;7;11;15} = {3; 7}