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\(\frac{A}{\sqrt{2}}=\frac{1+\sqrt{7}}{2+\sqrt{8+2\sqrt{7}}}+\frac{1-\sqrt{7}}{2-\sqrt{8-2\sqrt{7}}}\)
\(=\frac{1+\sqrt{7}}{2+1+\sqrt{7}}+\frac{1-\sqrt{7}}{2-\sqrt{7}+1}\)
\(=\frac{1+\sqrt{7}}{3+\sqrt{7}}+\frac{1-\sqrt{7}}{3-\sqrt{7}}\)
=\(\frac{\left(1+\sqrt{7}\right)\left(3-\sqrt{7}\right)+\left(1-\sqrt{7}\right)\left(3+\sqrt{7}\right)}{\left(3+\sqrt{7}\right)\left(3-\sqrt{7}\right)}\)
\(=\frac{-8}{2}=-4\)
\(\Rightarrow A=-4\sqrt{2}\)
Ta có : \(x=\frac{1}{2}\sqrt{\frac{\sqrt{2}-1}{\sqrt{2}+1}}=\frac{1}{2}\sqrt{\frac{\left(\sqrt{2}-1\right)^2}{\left(\sqrt{2}+1\right)\left(\sqrt{2}-1\right)}}=\frac{1}{2}\sqrt{\left(\sqrt{2}-1\right)^2}=\frac{\sqrt{2}-1}{2}\)
Thay \(x=\frac{\sqrt{2}-1}{2}\)vào \(4x^5+4x^4-5x^3+5x-2\)được kết quả bằng -1
\(\Rightarrow A=\left(-1\right)^{2012}+2103=1+2103=2104\)
Ta có : \(x=\dfrac{\sqrt{2}}{\sqrt{3}+\sqrt{2}}\sqrt{\dfrac{3\sqrt{2}+2\sqrt{3}}{3\sqrt{2}-2\sqrt{3}}}\)
\(=\dfrac{\sqrt{2}}{\sqrt{3}+\sqrt{2}}\sqrt{\dfrac{\sqrt{6}\left(\sqrt{3}+\sqrt{2}\right)}{\sqrt{6}\left(\sqrt{3}-\sqrt{2}\right)}}\)
\(=\dfrac{\sqrt{2}}{\sqrt{3}+\sqrt{2}}.\dfrac{\sqrt{\sqrt{3}+\sqrt{2}}}{\sqrt{\sqrt{3}-\sqrt{2}}}\)
\(=\dfrac{\sqrt{2}}{\sqrt{\left(\sqrt{3}+\sqrt{2}\right)\left(\sqrt{3}-\sqrt{2}\right)}}\)
\(=\dfrac{\sqrt{2}}{\sqrt{1}}=\sqrt{2}\)
Thay \(x=\sqrt{2}\) vào biểu thức A ta được :
\(A=\left(\sqrt{2}^3-2\sqrt{2}+1\right)^{2012}=1^{2012}=1\)
Vậy \(A=1\)
\(a^3+b^3=\sqrt{\left(\sqrt{6}-\sqrt{2}\right)^2}-\frac{4\left(\sqrt{6}-\sqrt{2}\right)}{6-2}=0\)
\(\Rightarrow a=-b\Rightarrow a^5+b^5=0\)
Ta có:
\(x=\sqrt{3+\sqrt{5+2\sqrt{3}}}+\sqrt{3-\sqrt{5+2\sqrt{3}}}\) ( x> 0 )
\(\Rightarrow x^2=6+2\sqrt{\left(3+\sqrt{5+2\sqrt{3}}\right)\left(3-\sqrt{5+2\sqrt{3}}\right)}\)
\(=6+2\sqrt{9-5-2\sqrt{3}}\)
\(=6+2\sqrt{\left(\sqrt{3}-1\right)^2}\)
\(=6+2\sqrt{3}-2=4+2\sqrt{3}=\left(\sqrt{3}+1\right)^2\)
\(\Rightarrow x=\sqrt{3}+1\)
Vậy :
\(A=x^2-2x-2=4+2\sqrt{3}-2\sqrt{3}-2-2\)
\(=0\)
Ta có:
\(x=\frac{1}{2}.\sqrt{\frac{\sqrt{2}-1}{\sqrt{2}+1}}=\frac{\sqrt{2}-1}{2}\)
\(\Rightarrow x\left(x+1\right)=\frac{\sqrt{2}-1}{2}.\frac{\sqrt{2}+1}{2}=\frac{1}{4}\)
Thế vô bài toán ta được
\(A=\left(4x^5+4x^4-5x^3+5x-2\right)^{2016}+2017\)
\(=\left(4x^4\left(x+1\right)-5x^3+5x-2\right)^{2016}+2017\)
\(=\left(-4x^3+5x-2\right)^{2016}+2017\)
\(=\left(\left(-4x^3-4x^2\right)+\left(4x^2+4x\right)+x-2\right)^{2016}+2017\)
\(=\left(-x+1+x-2\right)^{2016}+2017\)
\(=\left(-1\right)^{2016}+2017=2018\)
