Răspuns :
[tex]\it D_{12}=\{1,\ \ 2,\ \ 3,\ \ 4,\ \ 6,\ \ 12\}\\ \\ D_{28}=\{1,\ \ 2,\ \ 4,\ \ 7,\ \ 14,\ \ 28\}\\ \\ \\ D_{12}\cap D_{28}=\{1,\ \ 2,\ \ 4\}[/tex]
[tex]\it D_{12}=\{1,\ \ 2,\ \ 3,\ \ 4,\ \ 6,\ \ 12\}\\ \\ D_{28}=\{1,\ \ 2,\ \ 4,\ \ 7,\ \ 14,\ \ 28\}\\ \\ \\ D_{12}\cap D_{28}=\{1,\ \ 2,\ \ 4\}[/tex]