Tình nhanh \(49.15 - 49.5\) ta được kết quả là

\(A = \left[ {0;1;2;3} \right]\)   

\(A = \left( {0;1;2;3} \right)\)          

\(A = 1;2;3\)      

\(A = \left\{ {0;1;2;3} \right\}\)

${\rm{\{ 1;3\} }}$                      

${\rm{\{ 0;3\} }}$                         

${\rm{\{ 1;5\} }}$                              

${\rm{\{ 1;3;9\} }}$

$x \in \;\left\{ {5;15} \right\}$                       

$x\; \in \left\{ {30;60} \right\}$          

$x\; \in \left\{ {15;20} \right\}$               

$x\; \in \left\{ {20;30;60} \right\}$

\(a \vdots 2\)

\(b \vdots 2\)

\(\left( {a + b} \right) \vdots 2\)

\(\left( {a + b} \right)\not  \vdots 2\)

Chia cho \(5\) dư \(1.\)

Chia cho \(5\) dư \(4.\)

Chia cho \(5\) dư \(3.\)

Chia hết cho \(5.\)

\(a < 15\)

\(0 < a\)

\(0 < a < 15\)

\(2 < a < 10\)