Question

Giải chi tiết

Answer 1

\(BT1:\)

\(a,A=\left\{x\in B\left(30\right)|100\le x\le450\right\}\)

  Ta có : \(B\left(30\right)=\left\{0;30;60;90;120;150;180;210;240;270;300;330;360;390;420;...\right\}\)

Theo đề bài : \(x\in B\left(30\right)|100\le x\le450\) nên \(x\in\left\{0;30;60;90;120;150;180;210;240;270;300;330;360;390\right\}\)

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\(b,B=\left\{x\inƯ\left(48\right)|11< x\le24\right\}\)

Ta có : \(Ư\left(48\right)=\left\{1;2;3;4;6;8;12;16;24;48\right\}\)

Theo đề bài : \(x\inƯ\left(48\right)|11< x\le24\) nên \(x\in\left\{12;16;24\right\}\)

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\(BT2:\)

\(2021\)* chia hết cho 3 :

\(+>TH1:\) * \(=1\) thì \(20211⋮3\) vì  \(2+0+2+1+1=6⋮3\)

\(+>TH2:\) * \(=4\) thì \(20214⋮3\) vì \(2+0+2+1+4=9⋮3\)

Vậy * \(=1\) hoặc * \(=4\)