1: \(A=\left(\dfrac{\sqrt{x}\left(x\sqrt{x}-1\right)}{x+\sqrt{x}+1}-\dfrac{\sqrt{x}\left(2\sqrt{x}+1\right)}{\sqrt{x}}+\dfrac{2\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}{\sqrt{x}-1}\right)\cdot\dfrac{2}{x-\sqrt{x}+1}\)
\(=\left(\sqrt{x}\left(\sqrt{x}-1\right)-2\sqrt{x}-1+2\sqrt{x}+2\right)\cdot\dfrac{2}{x-\sqrt{x}+1}\)
\(=\left(x-\sqrt{x}+1\right)\cdot\dfrac{2}{x-\sqrt{x}+1}=2\)
2: \(x-\sqrt{3}=2\)
=>x=2+căn 3
=>x^2-4x=(2+căn 3)^2-4(2+căn 3)
=7+4căn 3-8-4căn 3
=-1
B=6(-1)^50+(-1)^25+2015
=6-1+2015
=2015+5=2020
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