Đại số 8

T

transformers123

$\dfrac{x^2+y^2}{xy}=\dfrac{25}{12}$

$\iff 12x^2+12y^2=25xy$

$\iff (4x-3y)(3x-4y)=0$

$\iff 4x-3y=0$ (vô lí) hoặc $3x-4y=0$

$\iff x=\dfrac{4y}{3}$

$\Longrightarrow \dfrac{x-y}{x+y} =\dfrac{\dfrac{4y}{3}-y}{\dfrac{4y}{3}+y}=\dfrac{1}{7}$
 
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