Salut!
a) [tex]D_{20}[/tex] = {1; 2; 4; 5; 10}
[tex]D_{45}[/tex] = {1; 3; 5; 9; 15; 45}
[tex]D_{20}[/tex] ∩ [tex]D_{45}[/tex] = {1; 5}
b) [tex]D_{18}[/tex] = {1; 2; 3; 6; 9; 18}
[tex]D_{24}[/tex] = {1; 2; 3; 4; 6; 8; 12; 24}
[tex]D_{18}[/tex] ∩ [tex]D_{24}[/tex] = {1; 2; 3; 6}
c) [tex]D_{15}[/tex] = {1; 3; 5; 15}
[tex]D_{30}[/tex] = {1; 2; 3; 5; 6; 10; 15; 30}
[tex]D_{48}[/tex] = {1; 2; 3; 6; 8; 12; 16; 24; 48}
[tex]D_{15}[/tex] ∩ [tex]D_{30}[/tex] ∩ [tex]D_{48}[/tex] = {1; 3}
d) [tex]D_{60}[/tex] = {1; 2; 3; 4; 5; 6; 10; 12; 15; 20; 30; 60}
[tex]D_{90}[/tex] = {1; 2; 3; 5; 6; 9; 10; 15; 18; 30; 45; 90}
[tex]D_{120}[/tex] = {1; 2; 3; 4; 5; 6; 8; 10; 12; 15; 20; 24; 30; 40; 60; 120}
[tex]D_{60}[/tex] ∩ [tex]D_{90}[/tex] ∩ [tex]D_{120}[/tex] = {1; 2; 3; 5; 6; 10; 15; 30}
-Luke48
