a)
[tex]3x^2\geq1\\\\3x^2-1\geq0\\\\(\sqrt3x-1)(\sqrt3+1)\geq0\\\\(\sqrt3x-1)(\sqrt3+1)=0\\\\\sqrt3x-1=0\ \vee\ \sqrt3+1=0\\\\\sqrt3x=1\ /\ :\ \sqrt3\ \vee\ \sqrt3x=-1\ /\ :\ \sqrt3\\\\x=\frac{1}{\sqrt3}=\frac{\sqrt3}{3}\ \vee\ x=-\frac{1}{\sqrt3}=-\frac{\sqrt3}{3}\\\\x\ \in\ (\ -\infty\ ;\ -\frac{\sqrt3}{3} > \ \cup\ < \frac{\sqrt3}{3}\ ;\ +\infty)[/tex]
b)
[tex]-4x^2\leq12x\\\\-4x^2-12x\leq0\ /\ :\ (-4)\\\\x^2+3\geq0\\\\x\ \in\ R[/tex]
