3x+2-\(\sqrt{9x^2+6x+1}\)( x>\(\frac{1}{3}\))
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a/ \(\frac{\sqrt{x^2-4x+4}}{x-2}=\frac{\sqrt{\left(x-2\right)^2}}{x-2}=\frac{\left|x-2\right|}{x-2}\)
có x<2\(\Rightarrow\left|x-2\right|=2-x\)
\(\Rightarrow\frac{2-x}{x-2}\)
b/ \(\frac{\sqrt{9x^2-6x+1}}{9x^2-1}=\frac{\sqrt{\left(3x-1\right)^2}}{\left(3x-1\right)\left(3x+1\right)}=\frac{\left|3x-1\right|}{\left(3x-1\right)\left(3x+1\right)}\)
Có x>\(\frac{1}{3}\Rightarrow\left|3x-1\right|=3x-1\)
\(\Rightarrow\frac{3x-1}{\left(3x-1\right)\left(3x+1\right)}=\frac{1}{3x+1}\)
b)
)\(\sqrt{\frac{4}{\left(2-\sqrt{5}\right)^2}}-\sqrt{\frac{4}{\left(2+\sqrt{5}\right)^2}}\)
= \(\frac{2}{2-\sqrt{5}}-\frac{2}{2+\sqrt{5}}\)
=\(\frac{2\left(2+\sqrt{5}\right)-2\left(2-\sqrt{5}\right)}{\left(2-\sqrt{5}\right)\left(2+\sqrt{5}\right)}\)
=\(\frac{4+2\sqrt{5}-4+2\sqrt{5}}{2^2-\sqrt{5}^2}\)
=\(\frac{4\sqrt{5}}{4-5}\)
=\(\frac{4\sqrt{5}}{-1}\)
\(-4\sqrt{5}\)
a/ \(\Rightarrow\sqrt{\left(3x+1\right)^2}=1\Rightarrow3x+1=1\Rightarrow3x=0\Rightarrow x=0\)
b/ \(\Rightarrow\frac{3}{2}\sqrt{3x}-\sqrt{3x}-\frac{1}{2}\sqrt{3x}=5\)
\(\Rightarrow\sqrt{3x}\left(\frac{3}{2}-1-\frac{1}{2}\right)=5\)
\(\Rightarrow\sqrt{3x}.0=5\Rightarrow0=5\) (vô lí)
Vậy pt vô nghiệm
\(3x+2-\sqrt{9x^2+6x+1}\)
\(=3x+2-\sqrt{\left(3x+1\right)^2}\)
\(=3x+2-\left(3x+1\right)\)(Chú ý \(x>\frac{1}{3}\))
\(=3x+2-3x-1=1\)