15 = 3.5
180 = 2².3².5
165 = 3.5.11
ƯCLN(15; 180; 165) = 3.5 = 15
ƯC(15; 180; 165) = {1; 3; 5; 15}
Ta có:
\(15=3\cdot5\\180=2^2\cdot3^2\cdot5\\165=3\cdot5\cdot11\\\Rightarrow UCLN(15;180;165)=3\cdot5=15\)
\(\Rightarrow UC\left(15;180;165\right)=U\left(15\right)=\left\{1;3;5;15\right\}\)