Đáp án:
c. \(\left\{ \begin{array}{l}
y = 5\\
x = 3
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\left\{ \begin{array}{l}
y = \left( {\sqrt 2 + 1} \right)x - \sqrt 2 \\
x + \left( {\sqrt 2 - 1} \right)\left[ {\left( {\sqrt 2 + 1} \right)x - \sqrt 2 } \right] = 1\left( * \right)
\end{array} \right.\\
\left( * \right) \to x + \left( {2 - 1} \right)x - \sqrt 2 \left( {\sqrt 2 - 1} \right) = 1\\
\to 2x - 2 + \sqrt 2 = 1\\
\to 2x = 3 - \sqrt 2 \\
\to x = \dfrac{{3 - \sqrt 2 }}{2}\\
\to y = \dfrac{1}{2}\\
b.\left\{ \begin{array}{l}
3x - 2y = - 8\\
- 4x + 2y = 10
\end{array} \right.\\
\to \left\{ \begin{array}{l}
3x - 4x = - 8 + 10\\
y = 5 + 2x
\end{array} \right.\\
\to \left\{ \begin{array}{l}
- x = 2\\
y = 5 + 2x
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = - 2\\
y = 1
\end{array} \right.\\
c.DK:x;y \ne 0\\
\left\{ \begin{array}{l}
\dfrac{3}{x} + \dfrac{3}{y} = \dfrac{8}{5}\\
\dfrac{3}{x} + \dfrac{5}{y} = 2
\end{array} \right.\\
\to \left\{ \begin{array}{l}
\dfrac{5}{y} - \dfrac{3}{y} = 2 - \dfrac{8}{5}\\
\dfrac{3}{x} + \dfrac{5}{y} = 2
\end{array} \right.\\
\to \left\{ \begin{array}{l}
\dfrac{2}{y} = \dfrac{2}{5}\\
\dfrac{3}{x} + \dfrac{5}{y} = 2
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = 5\\
x = 3
\end{array} \right.
\end{array}\)
