[tex]\lim(\sqrt{x^{2}+x+1}-2\sqrt{x^{2}-x}+x)=lim(\sqrt{x^2+x+1}-x+2x-2\sqrt{x^2-x})=lim(\frac{x+1}{\sqrt{x^2+x+1}+x}+2.\frac{x}{x+\sqrt{x^2-x}})=lim(\frac{1+\frac{1}{x}}{\sqrt{1+\frac{1}{x}+\frac{1}{x^2}}+1}+2.\frac{1}{1+\sqrt{1-\frac{1}{x}}})=\frac{3}{2}[/tex]