$\frac{1}{3(1-\sqrt{3}x)}+\frac{2\sqrt{3}}{1-3x^2} = \frac{\sqrt{3}}{3(1+\sqrt{3}x)}$
Nota che $(1-\sqrt{3}x)(1+\sqrt{3}x)=1-3x^2$, quindi:
$1+\sqrt{3}x+6\sqrt{3}=\sqrt{3}-3x$
$x(3+\sqrt{3})=-(5\sqrt{3}+1)$
$x=-\frac{5\sqrt{3}+1}{3+\sqrt{3}}$
$x=-\frac{15\sqrt{3}-15+3-\sqrt{3}}{6}=\frac{12-14\sqrt{3}}{6}=\frac{6-7\sqrt{3}}{3}$