Tìm các số hữu tỉ x,y,z biết các số đó thõa mãn các điều kiện: xy= 1/3 yz= -2/5 xz= -3/10

 Theo đề ra , ta có : 
`x.y.y.z.x.z=1/3 . (-2/5).(-3/10)`
`=>.y.y.z.x.z=1/25`
`=>(x.y.z)²=1/25`
`=>`  \(\left[ \begin{array}{l}x.y.z=\dfrac{1}{5}\\x.y.z=-\dfrac{1}{5}\end{array} \right.\) 
+ Nếu `x.y.z=1/5` thì :
`=>`  \(\left[ \begin{array}{l}x=\dfrac{1}{5}:\dfrac{1}{3}\\y=\dfrac{1}{5}:(-\dfrac{2}{5})\\z=\dfrac{1}{5}:(-\dfrac{3}{10})\end{array} \right.\) 
`=>` \(\left[ \begin{array}{l}x=\dfrac{3}{5}\\y=-\dfrac{1}{2}\\z=-\dfrac{2}{3}\end{array} \right.\) 
+ Nếu `x.y.z=-1/5` thì :
`=>`  \(\left[ \begin{array}{l}x=(-\dfrac{1}{5}):\dfrac{1}{3}\\y=(-\dfrac{1}{5}):(-\dfrac{2}{5})\\z=(-\dfrac{1}{5}):(-\dfrac{3}{10})\end{array} \right.\) 
`=>` \(\left[ \begin{array}{l}x=-\dfrac{3}{5}\\y=\dfrac{1}{2}\\z=\dfrac{2}{3}\end{array} \right.\) 
Vậy `(x;y;z)=(3/5:-1/2;-2/3),(-3/5;1/2;2/3)`