Gọi 2 số đó là a và b ( \(a,b\ne0\) )
Theo đề bài ta có hệ:
\(\left\{{}\begin{matrix}a+b=7\\\frac{1}{a}+\frac{1}{b}=\frac{7}{12}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}b=7-a\\\frac{1}{a}+\frac{1}{7-a}=\frac{7}{12}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}a=3\\b=7-a\end{matrix}\right.\\\left\{{}\begin{matrix}a=4\\b=7-a\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}a=3\\b=4\end{matrix}\right.\\\left\{{}\begin{matrix}a=4\\b=3\end{matrix}\right.\end{matrix}\right.\)
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