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b.$x^{4}$+$\sqrt{x^{2}+2005}$=2005
<=>$x^{4}$+$x^{2}$+$\frac{1}{4}$=$x^{2}$+2005-$\sqrt{x^{2}+2005}$+$\frac{1}{4}$
<=>$(x^{2}+\frac{1}{2})^{2}$-$(\sqrt{x^{2}+2005}-\frac{1}{2})^{2}$=0
<=>($x^{2}$+$\sqrt{x^{2}+2005}$)($x^{2}$-$\sqrt{x^{2}+2005}$+1)=0
<=>$x^{2}$-$\sqrt{x^{2}+2005}$+1=0($x^{2}$+$\sqrt{x^{2}+2005}$$\ne$0)
<=>$x^{2}$+2005-$\sqrt{x^{2}+2005}$+$\frac{1}{4}$=$\frac{8017}{4}$
<=>$(\sqrt{x^{2}+2005}-\frac{1}{2})^{2}$=$\frac{8017}{4}$
<=>$\sqrt{x^{2}+2005}$=$\pm$$\frac{\sqrt{8017}}{2}$+$\frac{1}{2}$
<=>$\sqrt{x^{2}+2005}$=$\frac{\sqrt{8017}}{2}$+$\frac{1}{2}$ ($\sqrt{x^{2}+2005}$>0)
<=>$x^{2}$=$\frac{-1+\sqrt{8017}}{2}$
<=>$x$=$\pm$$\sqrt{\frac{-1+\sqrt{8017}}{2}}$
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