Có bao nhiêu số nguyên $a < 5$ biết: $10$ là bội của $\left( {2a + 5} \right)$

\(\left( {a + b} \right) + c = a + \left( {b + c} \right);\)

\(a + b = b + a\)

\(a + \left( { - a} \right) = \left( { - a} \right) + a = 0.\)

\( - 13\) 

\(5\)

\( - 23\)

\(23\)

\(D = \left\{ { - 3; - 2;0} \right\}.\)

\(D = \left\{ { - 3; - 2} \right\}.\)  

\(D = \left\{ {0;1;6;10} \right\}.\)                          

\(D = \left\{ { - 3; - 2;6;10;1} \right\}.\)

$40$                         

$10$                            

$50$                          

$30$

\( - 6;\,\;6;\;\,0;\,\;23;\, - 23\)

\(132;\, - 132;\;\,16\)  

\( - 1;\,\;1;\,\;6;\, - 6\)  

\(0;\;\,6;\, - 6;\;\,12;\, - 12;\,...\)