tìm ab sao cho a765b chia hết cho 3 và 5 mình cần giải chi tiết

\[\begin{array}{l} \overline {a765b} \,\,\left( {a \ne 0} \right)\,\,\,chia\,\,het\,\,cho\,\,5 \Rightarrow b \in \left\{ {0;\,\,5} \right\}\\ + )\,\,\,\,Voi\,\,\,b = 5 \Rightarrow so\,\,\,can\,\,tim:\,\,\,\overline {a7655} \\ Ta\,\,\,\,co\,:\,\,\,a + 7 + 6 + 5 + 5 = 23 + a\\ \overline {a7655} \,\,\, \vdots \,\,\,3 \Rightarrow \left[ \begin{array}{l} 23 + a = 24\\ 23 + a = 27\\ 23 + a = 30 \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} a = 1\\ a = 4\\ a = 7 \end{array} \right.\\ \Rightarrow So\,\,\,can\,\,tim:\,\,\,17655;\,\,\,47655;\,\,\,77655.\\ + )\,\,Voi\,\,\,b = 0 \Rightarrow so\,\,\,can\,\,tim:\,\,\,\overline {a7650} \\ Ta\,\,\,\,co\,:\,\,\,a + 7 + 6 + 5 + 0 = 18 + a\\ \overline {a7655} \,\,\, \vdots \,\,\,3 \Rightarrow \left[ \begin{array}{l} 18 + a = 18\\ 18 + a = 21\\ 18 + a = 24\\ 18 + a = 27 \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} a = 0\,\,\,\,\left( {ktm} \right)\\ a = 3\\ a = 6\\ a = 9 \end{array} \right.\\ \Rightarrow So\,\,\,can\,\,tim:\,\,\,37650;\,\,\,67650;\,\,\,97650. \end{array}\]