Đáp án:
Áp dụng tính chất dãy tỉ số bằng nhau ta có:
$\begin{array}{l}
3)\\
3x = 2y;y = 2z\\
\Rightarrow y = \dfrac{{3x}}{2}\\
\Rightarrow \dfrac{{3x}}{2} = y = 2z\\
\Rightarrow \dfrac{{3x}}{{2.6}} = \dfrac{y}{6} = \dfrac{{2z}}{6}\\
\Rightarrow \dfrac{x}{4} = \dfrac{y}{6} = \dfrac{z}{3} = \dfrac{{2x}}{8} = \dfrac{{3y}}{{18}} = \dfrac{{2z}}{6}\\
= \dfrac{{2x + 3y - 2z}}{{8 + 18 - 6}} = \dfrac{{40}}{{20}} = 2\\
\Rightarrow \left\{ \begin{array}{l}
x = 2.4 = 8\\
y = 2.6 = 12\\
z = 2.3 = 6
\end{array} \right.\\
Vay\,x = 8;y = 12;z = 6\\
4)x = 3y = 2z\\
\Rightarrow \dfrac{x}{6} = \dfrac{{3y}}{6} = \dfrac{{2z}}{6}\\
\Rightarrow \dfrac{x}{6} = \dfrac{y}{2} = \dfrac{z}{3} = \dfrac{{2x}}{{12}} = \dfrac{{3y}}{6} = \dfrac{{4z}}{{12}}\\
= \dfrac{{2x - 3y + 4z}}{{12 - 6 + 12}} = \dfrac{{48}}{{18}} = \dfrac{8}{3}\\
\Rightarrow \left\{ \begin{array}{l}
x = \dfrac{8}{3}.6 = 16\\
y = \dfrac{8}{3}.2 = \dfrac{{16}}{3}\\
z = \dfrac{8}{3}.3 = 8
\end{array} \right.\\
Vay\,x = 16;y = \dfrac{{16}}{3};z = 8
\end{array}$
