a). D12={1,2,3,4,6,12}
2x+1=1, 2x=0, x=0 apartine N
2x+1=2, 2x=1, x=1/2 nu apartine N
2x+1=3, 2x=2, x=1 apartine N
2x+1=4, 2x=3, x=3/2 nu apartine N
2x+1=6, 2x=5, x=5/2 nu apartine N
2x+1=12, 2x=11, x=11/2 nu apartine N
Pe scurt, S={0,1}
b). Divizorii proprii ai lui 6 sunt 2 si 3.
x+1=2, x=1
x+1=3, x=2
S={1,2}