`2x^2 +2y^2 =5xy`
`=> 2x^2 -5xy +2y^2 = 0`
`=> 2x^2 - xy - 4xy + 2y^2= 0`
`=> (2x^2 - xy) - (4xy -2y^2)=0`
`=> x. (2x - y) - 2y. (2x - y) = 0`
`=> (2x - y). (x -2y) = 0`
`=>` \(\left[ \begin{array}{l}2x-y=0\\x-2y=0\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}2x=y\\x=2y\end{array} \right.\) mà `y > x > 0`
`=> 2x =y`
`=> (x + y)/(x - y) = (x + 2x)/(x - 2x) = (3x)/(-x) = -3`
Vậy `(x + y)/(x - y) = -3`
