mik viết nhầm
\(\overline{31xy}\) \(⋮\)2;5 \(\Rightarrow\)y \(\in\)\(\left\{0\right\}\)
nếu y = 0 ta có : \(\overline{31x0}\)\(⋮\) 3
\(\Rightarrow\) ( 3 + 1 +x + 0 ) \(⋮\) 3
\(\Rightarrow\) (4 + x )\(⋮\) 3
\(\Rightarrow\) x \(\in\)\(\left\{2;5;8\right\}\)
\(\Rightarrow\)\(\overline{31xy}\) = 3120 ; 3150 ; 3180
Để \(\overline{31xy}\) \(_⋮\)2,5 => y \(\in\) \(\in\)
Nếu y = 0 ta có : \(\overline{31x0}\)\(⋮\)3
=> ( 3 + 1 + x + 0 ) \(⋮\)3
=> 4 + x \(⋮\)3
=> x \(\in\) \(\left\{2,5,8\right\}\)
\(_{\Rightarrow}\)\(\overline{31xy}\) = 3120 ;3150 ; 3180
