Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}a)\,\frac{x}{3} = \frac{y}{5}\,\,\,va\,\,\,x - y = 4\\ \Rightarrow \frac{x}{3} = \frac{y}{5} = \frac{{x - y}}{{3 - 5}} = \frac{4}{{ - 2}} = 2\\ \Rightarrow \left\{ \begin{array}{l}x = 2.3 = 6\\y = 5.2 = 10\end{array} \right.\end{array}\)
\(\begin{array}{l}b)\,\frac{x}{2} = \frac{y}{3} = z\,\,\,\,va\,\,\,2x + y - 3z = - 8\\ \Rightarrow \,\frac{x}{2} = \frac{y}{3} = \frac{z}{1}\\ \Leftrightarrow \frac{{2x}}{4} = \frac{y}{3} = \frac{{ - 3z}}{{ - 3}} = \frac{{2x + y - 3z}}{{4 + 3 - 3}} = \frac{{ - 8}}{4} = - 2\\ \Leftrightarrow \left\{ \begin{array}{l}x = \frac{{ - 2.4}}{2} = - 4\\y = - 2.3 = - 6\\z = - 2\end{array} \right.\end{array}\)
