Giải thích các bước giải:
\(\begin{array}{l}
a)\left\{ \begin{array}{l}
y = \sqrt 5 x - 5 + \sqrt 5 \\
2\sqrt 3 x + 3\sqrt 5 \left( {\sqrt 5 x - 5 + \sqrt 5 } \right) = 21
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
y = \sqrt 5 x - 5 + \sqrt 5 \\
2\sqrt 3 x + 15x - 15\sqrt 5 + 15 = 21
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
y = \sqrt 5 x - 5 + \sqrt 5 \\
\left( {2\sqrt 3 + 15} \right)x = 6 + 15\sqrt 5
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
x = \dfrac{{6 + 15\sqrt 5 }}{{2\sqrt 3 + 15}}\\
y = \dfrac{{6\sqrt 5 + 75}}{{15 + 2\sqrt 3 }} - 5 + \sqrt 5
\end{array} \right.\\
b)\left\{ \begin{array}{l}
y = 3x - 3\sqrt 2 + \sqrt 3 \\
2\sqrt 3 x - \sqrt 5 \left( {3x - 3\sqrt 2 + \sqrt 3 } \right) = 2\sqrt 6
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
y = 3x - 3\sqrt 2 + \sqrt 3 \\
2\sqrt 3 x - 3\sqrt 5 x + 3\sqrt {10} - \sqrt {15} = 2\sqrt 6
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
y = 3x - 3\sqrt 2 + \sqrt 3 \\
\left( {2\sqrt 3 - 3\sqrt 5 } \right)x = \sqrt {15} + 2\sqrt 6 - 3\sqrt {10}
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
x = \dfrac{{\sqrt {15} + 2\sqrt 6 - 3\sqrt {10} }}{{2\sqrt 3 - 3\sqrt 5 }}\\
y = \dfrac{{3\sqrt {15} + 6\sqrt 6 - 9\sqrt {10} }}{{2\sqrt 3 - 3\sqrt 5 }} - 3\sqrt 2 + \sqrt 3
\end{array} \right.
\end{array}\)
các câu sau em làm tương tự nhé
