Em tham khảo:
$\dfrac{1}{5}-$ $|\dfrac{1}{5-x}|=$$\dfrac{1}{5}$
⇔$|\dfrac{1}{5-x}|=$$\dfrac{1}{5}+$$\dfrac{1}{5}$
⇔$|\dfrac{1}{5-x}|=$$\dfrac{2}{5}$
Vì $\dfrac{2}{5}>0$
⇒$\dfrac{1}{5-x}=$$\dfrac{2}{5}$
⇔$2(5-x)=5$
⇔$x=$$\dfrac{5}{2}$ (thõa mãn)
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