Question

bài 2:viết các tập hợp

a)Ư(12):Ư(18);ƯC(12,18)

b)B(15);B(21);BC(15,21)

c)BC(20;24;28)

Answer 1

a) 

\(Ư\left(12\right)=\left\{1;2;3;4;6;12\right\}\)

\(Ư\left(18\right)=\left\{1;2;3;6;9;18\right\}\)

=> \(ƯC\left(12;18\right)=\left\{1;2;3;6;\right\}\)

b) \(B\left(15\right)=\left\{0;15;30;45;60;90;105...\right\}\)

   \(B\left(21\right)=\left\{0;21;42;63;84;105;...\right\}\)

=> \(BC\left(15;21\right)=\left\{0;105;...\right\}\)

 c)

 \(20=2^2.5\)

\(24=2^3.3\)

\(28=2^2.7\)

=> \(BCNN\left(20;24;28\right)=2^3.3.5.7=840\)

=> \(BC\left(20;24;28\right)=B\left(840\right)=\left\{0;840;1680;...\right\}\)