`a)` - Ta có :
`144=2^4 .3^2`
`180=2^2 .3^2 .5`
`192=2^6 .3`
`=> ƯC LN(144,180,192)=2^2 .3=12`
`=> ƯC(144,180,192)=Ư(12)={1;2;3;4;6;12}`
`b)` - Ta có :
`350=2.5^2 .7`
`420=2^2 .3.5.7`
`560=2^4 .5.7`
`=> ƯC LN(350,420,560)=2 .5.7=70`
`=> ƯC(350,420,560)=Ư(70)={1;2;5;7;10;14;35;70}`
`c)` - Ta có :
`24=2^3 .3`
`78=2.3.13`
`42=2.3.7`
`=> ƯC LN(24,78,42)=2.3=6`
`=> ƯC(24,78,42)=Ư(6)={1;2;3;6}`
`d)` - Ta có :
`15=3.5`
`9=3^2`
`45=3^2 .5`
`=> BCN N(15,9,45)=3^2 .5=45`
`=> BC(15,9,45)=B(45)={0;45;90;135;180;...}`