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bài 1
P=\(\left(\frac{x+2}{x\sqrt{x}-1}+\frac{\sqrt{x}}{x+\sqrt{x}+1}-\frac{1}{\sqrt{x}-1}\right)\)
=\(\left(\frac{x+2}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}+\frac{\sqrt{x}\left(\sqrt{x}-1\right)}{...}-\frac{\left(x+\sqrt{x}+1\right)}{...}\right):\frac{\sqrt{x}-1}{2}\)
=\(\left(\frac{x+2+x-\sqrt{x}-x-\sqrt{x}-1}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\right):\frac{\sqrt{x}-1}{2}\)
=\(\left(\frac{x-2\sqrt{x}+1}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\right):\frac{\sqrt{x}-1}{2}\)
=\(\left(\frac{\left(\sqrt{x}-1\right)^2}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\right):\frac{\sqrt{x}-1}{2}\)
=\(\frac{\sqrt{x}-1}{x+\sqrt{x}+1}.\frac{2}{\sqrt{x}-1}\)
=\(\frac{2}{x+\sqrt{x}+1}\)
P>0 dựa vào dkxd
Bài 1:
a) P= \(\left(\frac{x+2}{x\sqrt{x}-1}+\frac{\sqrt{x}}{x+\sqrt{x}+1}+\frac{1}{1-\sqrt{x}}\right):\frac{\sqrt{x}-1}{2}\) (x ≥ 0; x ≠ 4)
=\(\left(\frac{x+2}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}+\frac{\left(\sqrt{x}-1\right)\cdot\sqrt{x}}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}-\frac{x+\sqrt{x}+1}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}\right)\cdot\frac{2}{\sqrt{x}-1}\)
= \(\left(\frac{x+2+x-\sqrt{x}-x-\sqrt{x}-1}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}\right)\cdot\frac{2}{\sqrt{x}-1}\)
=\(\left(\frac{x-2\sqrt{x}+1}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}\right)\cdot\frac{2}{\sqrt{x}-1}\)
=\(\frac{\left(\sqrt{x}-1\right)^2\cdot2}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)\cdot\left(\sqrt{x}-1\right)}\)
=\(\frac{2}{x+\sqrt{x}+1}\)
b) Ta có: x ≥ 0 ⇒ \(\sqrt{x}\) ≥ 0
⇒ \(x+\sqrt{x}+1\) ≥ 1 > 0
mà 2 > 0 ⇒ \(\frac{2}{x+\sqrt{x}+1}\) > 0 ⇒ P > 0
Bài 2:
a) P= \(\left(\frac{2\sqrt{x}+x}{x\sqrt{x}-1}-\frac{1}{\sqrt{x}-1}\right):\left(1-\frac{\sqrt{x}+2}{x+\sqrt{x}+1}\right)\) (x ≥ 0; x ≠ 1)
=\(\left(\frac{2\sqrt{x}+x}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}-\frac{x+\sqrt{x}+1}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}\right):\left(\frac{x+\sqrt{x}+1}{x+\sqrt{x}+1}-\frac{\sqrt{x}+2}{x+\sqrt{x}+1}\right)\)
=\(\left(\frac{2\sqrt{x}+x-x-\sqrt{x}-1}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}\right):\left(\frac{x+\sqrt{x}+1-\sqrt{x}-2}{x+\sqrt{x}+1}\right)\)
=\(\left(\frac{\sqrt{x}-1}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}\right):\left(\frac{x-1}{x+\sqrt{x}+1}\right)\)
=\(\frac{\sqrt{x}-1}{\left(\sqrt{x}-1\right)\cdot\left(x+\sqrt{x}+1\right)}\cdot\frac{x+\sqrt{x}+1}{x-1}\)
=\(\frac{1}{x-1}\)
b) Ta có: \(\sqrt{P}=\sqrt{\frac{1}{x-1}}\)
= \(\frac{1}{\sqrt{x-1}}\)
x = \(5+2\sqrt{3}\) (TM)
Thay x vào \(\sqrt{P}\) ta có:
\(\sqrt{P}=\frac{1}{\sqrt{5+2\sqrt{3}-1}}\)
=\(\frac{1}{\sqrt{4+2\sqrt{3}}}\)
=\(\frac{1}{\sqrt{3+2\sqrt{x}+1}}\)
=\(\frac{1}{\sqrt{\left(\sqrt{3}+1\right)^2}}\)
=\(\frac{1}{\left|\sqrt{3}+1\right|}\)
=\(\frac{1}{\sqrt{3}+1}\)
= \(\frac{\sqrt{3}-1}{\left(\sqrt{3}+1\right)\cdot\left(\sqrt{3}-1\right)}\)
=\(\frac{\sqrt{3}-1}{2}\)
Vậy \(\sqrt{P}=\frac{\sqrt{3}-1}{2}\) khi x = \(5+2\sqrt{3}\)
Ta có
\(x=\frac{\sqrt{4+2\sqrt{3}}-\sqrt{3}}{\left(\sqrt{5}+2\right)\sqrt[3]{17\sqrt{5}-38}-2}\)
\(=\frac{\sqrt{3+2\sqrt{3}+1}-\sqrt{3}}{\left(\sqrt{5}+2\right)\sqrt[3]{5\sqrt{5}-3.5.2+3.4.\sqrt{5}-8}-2}\)
\(=\frac{\sqrt{3}+1-\sqrt{3}}{\left(\sqrt{5}+2\right)\left(\sqrt{5}-2\right)-2}=\frac{1}{5-4-2}=-1\)
Thế vào ta được
\(P=\left(x^2+x+1\right)^{2013}+\left(x^2+x-1\right)^{2013}\)
\(=\left(1-1+1\right)^{2013}+\left(1-1-1\right)^{2013}=1-1=0\)