5x=2y => \(\frac{x}{2}=\frac{y}{5}=>\frac{x}{6}=\frac{y}{15}\)
2y=3z => \(\frac{y}{3}=\frac{z}{2}=>\frac{y}{15}=\frac{z}{10}\)
=> \(\frac{x}{6}=\frac{y}{15}=\frac{z}{10}\)
=> \(\frac{x^2}{36}=\frac{x.y}{6.15}=\frac{90}{90}=1\)
=> x2 =36
=> x= -6;6
Xet x=-6
=> y= 90: (-6)=-15
=> z= -15:15.10=-10
Xet x=6
=> y=90:6=15
=> z=15:15.10=10
Vậy ( x;y;z) =( -6;-15;-10) ; ( 6;15;10)