Question

Thay ab(a khác b) bằng chữ số thích hợp để: 1a345 + 234b5 < 33770

Answer 1

\(1a345+234b5< 33770\)

=>\(\overline{3\left(a+3\right)7\left(4+b+1\right)0}< 33770\)

=>\(\left[{}\begin{matrix}a+3< 7\\\left\{{}\begin{matrix}a+3=7\\4+b+1< 7\end{matrix}\right.\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}a< 4\\\left\{{}\begin{matrix}a=4\\b< 2\end{matrix}\right.\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}a\in\left\{0;1;2;3\right\}\\\left\{{}\begin{matrix}a=4\\b\in\left\{0;1\right\}\end{matrix}\right.\end{matrix}\right.\)