Ta có: \(\frac{\sqrt{6+2\sqrt{5}}+\sqrt{6-2\sqrt{5}}}{\sqrt{20}}=\frac{\sqrt{\left(\sqrt{5}+1\right)^2}+\sqrt{\left(\sqrt{5}-1\right)^2}}{\sqrt{20}}\)
\(=\frac{\sqrt{5}+1+\sqrt{5}-1}{\sqrt{20}}=\frac{2\sqrt{5}}{2\sqrt{5}}=1\)
\(\Rightarrow P=\left(x^5-x^7-1\right)^{2017}=\left(1-1-1\right)^{2017}=-1\)
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