1)

C_1 : A = {4;5;6;7;8;9;10;11;12;13;14}

C_2 : A = {x |x \in NN, 3 < x < 15|}

2)

C_1: B = {7;8;9;10;11;12;13;14;15;16;17}

C_2: B= {xx|x \in NN, 6

3)

C_1 : C = {3;4;5;6;7;8}

C_2 : C ={x |x\in NN, 3 <= x <9|}

4)

C_1: D = {16;18;20}

C_2: D = {x|x  \in NN, x chẵn, 14 < x <21|}

a) C1: A = {4; 5; 6; 7;....; 14}

C2: A = {x|x$$\in$$N, 3$$\le$$x$$\le$$15}

b) C1: B = {7; 8; 9; .....; 17}

C2: B = {x|x$$\in$$N, 7$$\le$$x$$\le$$17}

c) C1: C = {3; 4; 5; ....; 8}

C2: C = {x|x$$\in$$N, 3$$\le$$x<8}

d) C1: D = {16; 18; 20}

C2: D = {x$$\in$$N|x$$\vdots$$2, 14$$\le$$x$$\le$$21}