Đáp án:
a. y=4;x=3
Giải thích các bước giải:
\(\begin{array}{l}
a.\left\{ \begin{array}{l}
x = 7 - y\\
\sqrt {7 - y + 1} + \sqrt y = 4\left( * \right)
\end{array} \right.\\
\left( * \right) \to \sqrt {8 - y} + \sqrt y = 4\\
\to \sqrt {8 - y} = 4 - \sqrt y \left( {DK:8 \ge y \ge 0} \right)\\
\to 8 - y = 16 - 8\sqrt y + y\\
\to 2y - 8\sqrt y + 8 = 0\\
\to \sqrt y = 2\\
\to y = 4\left( {TM} \right)\\
\to x = 3\\
d.DK:x \ne 1;y \ne 2;z \ne 3\\
\left\{ \begin{array}{l}
y - 2 = 2x - 2\\
2z - 6 = 3y - 6\\
x + 2y + 5z = 56
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = \dfrac{y}{2}\\
z = \dfrac{3}{2}y\\
\dfrac{y}{2} + y + 5.\dfrac{3}{2}y = 56
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = \dfrac{{56}}{9}\\
x = \dfrac{{28}}{9}\\
z = \dfrac{{28}}{3}
\end{array} \right.
\end{array}\)
