6, $\left\{ \begin{array}{l} 2x^2+x-1/y=2\\ y-y^2x-2y^2=-2 \end{array} \right.$
1, $\sqrt{2x^2+x+9}+\sqrt{2x^2-x+1}=x+4$ 2, $3\sqrt{x}+\frac{3}{2\sqrt{x}}<2x+\frac{1}{2x}-7$
3, $\frac{x-\sqrt{x}}{1-\sqrt{2(x^2-x+1)}}\geq 1 $
4, $\frac{\sqrt{x^2-16}}{\sqrt{x-3}}+\sqrt{x-3}>\frac{5}{\sqrt{x-3}}$
5. $\sqrt{3x^2+6x+4}<2-2x-x^2$