Giải thích các bước giải:
\(\begin{array}{l}
\left\{ \begin{array}{l}
21{\left( {x + 2} \right)^2} - 49\left( {x + y - 3} \right) = 301\\
21{\left( {x + 2} \right)^2} + 15\left( {x + y - 3} \right) = 45
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
7{\left( {x + 2} \right)^2} + 5\left( {x + y - 3} \right) = 15\\
64\left( {x + y - 3} \right) = - 256
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
x + y - 3 = - 4\\
7{\left( {x + 2} \right)^2} + 5.\left( { - 4} \right) = 15
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
{\left( {x + 2} \right)^2} = 5\\
y = - x - 1
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x = \sqrt 5 - 2\\
y = - \sqrt 5 + 1
\end{array} \right.\\
\left\{ \begin{array}{l}
x = - \sqrt 5 - 2\\
y = \sqrt 5 + 1
\end{array} \right.
\end{array} \right.
\end{array}\)
