Ta có : \(\frac{x+y}{3}=\frac{z+x}{2}=\frac{x+y-z-x}{3-2}=y-z\)
\(\frac{y+z}{3}=\frac{z+x}{5}=\frac{-y-z+z+x}{-3+5}=\frac{x-y}{2}\)
\(\frac{x-y}{2}=\frac{z+x}{5}\)\(\Rightarrow x-y=\frac{2.\left(z+x\right)}{5}\)\(\Rightarrow\frac{x-y}{4}=\frac{z+x}{10}\)( 1 )
\(\frac{z+x}{2}=y-z\)\(\Rightarrow\frac{y-z}{5}=\frac{z+x}{10}\) ( 2 )
Từ ( 1 ) và ( 2 ) suy ra : \(\frac{x-y}{4}=\frac{y-z}{5}\)