a) \(\overline{15a9b}⋮36\)
mà \(36=2^2.3^2\)
\(\Rightarrow\overline{15a9b}⋮2\&3\)
\(\overline{15a9b}⋮2\Rightarrow b\in\left\{0;2;4;6;8\right\}\)
\(\overline{15a9b}⋮3\Rightarrow1+5+a+9+b=a+b+15⋮3\Rightarrow a+b⋮3\)
\(\Rightarrow\left(a;b\right)=\left\{\left(3;0\right);\left(6;0\right);\left(9;0\right);\left(1;2\right);\left(4;2\right);\left(7;2\right);\left(2;4\right);\left(5;4\right);\left(8;4\right);\left(0;6\right);\left(3;6\right);\left(6;6\right);\left(9;6\right);\left(1;8\right);\left(4;8\right);\left(7;8\right)\right\}\)
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