Giải thích các bước giải:
a,
\(\begin{array}{l}
\left\{ \begin{array}{l}
x = 35\left( {y + 2} \right)\\
x = 50\left( {y - 1} \right)
\end{array} \right.\\
\Rightarrow 35\left( {y + 2} \right) = 50\left( {y - 1} \right)\\
\Leftrightarrow 35y + 70 = 50y - 50\\
\Leftrightarrow 15y = 120\\
\Leftrightarrow y = 8\\
\Rightarrow x = 35.\left( {y + 2} \right) = 35.\left( {8 + 2} \right) = 350\\
b,\\
\left\{ \begin{array}{l}
\left( {x + 14} \right)\left( {y - 2} \right) = xy\\
\left( {x - 4} \right)\left( {y + 1} \right) = xy
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
xy - 2x + 14y - 28 = xy\\
xy + x - 4y - 4 = xy
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
- x + 7y = 14\\
x - 4y = 4
\end{array} \right.\\
\Rightarrow \left( { - x + 7y} \right) + \left( {x - 4y} \right) = 14 + 4\\
\Leftrightarrow 3y = 18\\
\Leftrightarrow y = 6 \Rightarrow x = 28
\end{array}\)
