Bài 2:
\(\dfrac{x}{6}=\dfrac{-1}{y}\)
nên xy=-6
\(\Leftrightarrow\left(x,y\right)\in\left\{\left(1;-6\right);\left(-6;1\right);\left(-1;6\right);\left(6;-1\right);\left(2;-3\right);\left(-3;2\right);\left(3;-2\right);\left(-2;3\right)\right\}\)
Bài 3:
\(\dfrac{-1}{2}=\dfrac{x}{-3}=\dfrac{y}{4}=\dfrac{-3}{z}\)
=>x=3/2; y=-2; z=6