a)Có:40=2³.5
24=2³.3
=>UCLN(40,24)=8
=>ƯC(40,24)={±1;±2;±4;±8}
b)Có:12=2².3
52=2².13
=>UCLN(12,52)=4
=>ƯC(12,52)={±1;±2;±4}
c)Có:36=2².3²
990=2.3².5.11
=>UCLN(36,990)=18
=>ƯC(36,990)={±1;±2;±3;±6;±9;±18}
d)Có:80=2^4.5
144=2^4.3²
=>UCLN(80,144)=16
=>ƯC(80,144)={±1;±2;±8;±16}