Question

[Trần Long]

Tìm a, b
\(\overline{\text{a8520b}}\) chia hết cho 5, chia 3 dư 1.

Answer 1

[Trương Nhật Minh]

Ta có: 

\(\overline{a8520b}⋮5\Rightarrow\left[{}\begin{matrix}b=0\\b=5\end{matrix}\right.\)

Xét \(b=0\) 

\(\overline{a85200}:3\) dư 1 \(\Rightarrow\overline{a85200}-1⋮3\Rightarrow\overline{a85199}⋮3\)

\(\Rightarrow a+8+5+1+9+9=a+32⋮3\\ \Rightarrow a=1;4;7\)

Xét \(b=5\)

\(\overline{a85205}:3\) dư 1

  \(\Rightarrow\overline{a85205}-1⋮3\\ \Rightarrow\overline{a85204}⋮3\\ \Rightarrow a+8+5+2+0+4⋮3\\ \Rightarrow a+19⋮3\\ \Rightarrow a=2;5;8\)  

Đs....