2. rút gọn
\(x-2y-\sqrt{x^2-4xy+4y^2}\)
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\(=\frac{2x\left(x-2y\right)}{\left(x+2y\right)^2}:\frac{\left(2y-x\right)\left(2y+x\right)}{\left(x-2y\right)^2}:\frac{5xy\left(x-2y\right)}{\left(x+2y\right)^3}\)
Điều kiện: \(x\ne2y;x\ne-2y;x\ne0;y\ne0\)
\(=\frac{2x\left(x-2y\right)}{\left(x+2y\right)^2}:\frac{\left(2y+x\right)}{\left(x-2y\right)}:\frac{5xy\left(x-2y\right)}{\left(x+2y\right)^3}\)
\(=\frac{2x\left(x-2y\right)}{\left(x+2y\right)^2}\times\frac{x-2y}{x+2y}\times\frac{\left(x+2y\right)^3}{5xy\left(x-2y\right)}=\frac{2\left(x-2y\right)}{5y}\)
a: \(=\dfrac{\left|x+2\right|}{x-1}\)
b: \(=x-2y-\left|x-2y\right|\)\(=\left[{}\begin{matrix}x-2y-x+2y=0\\x-2y+x-2y=2x-4y\end{matrix}\right.\)
c: \(=\dfrac{\left|x+2\right|}{\left(x+2\right)\left(x-2\right)}=\pm\dfrac{1}{x-2}\)
\(x-2y-\sqrt{x^2-4xy+4y^2}\left(1\right)=x-2y-\sqrt{\left(x-2y\right)^2}=x-2y-\left|x-2y\right|\)
TH1: \(x\ge2y\)
\(\left(1\right)=x-2y-x+2y=0\)
TH2: \(x< 2y\)
\(\left(1\right)=x-2y+x-2y=2x-4y\)
= x - 2y - \(\sqrt{\left(x-2y\right)^2}\)
= x - 2y - /x-2y/
= x - 2y - x + 2y
= 0