EM tham khảo:
c/Với $A=$$\dfrac{1}{3}$
⇔$\dfrac{3x}{(x-2)(x+2)}=$ $\dfrac{1}{3}$
⇔$9x=$ $x^{2}-4$
⇔$x^{2}-9x-4=0$
⇔$x^{2}-2.x.$$\dfrac{9}{2}+$$\frac{81}{4}-$$\dfrac{-97}{4}=0$
⇔ $(x-\dfrac{9}{2})^{2}-\dfrac{97}{4}=0$
⇔\(\left[ \begin{array}{l}x=\dfrac{9+\sqrt{97}}{2}\\x=\dfrac{9-\sqrt{97}}{2}\end{array} \right.\)