\(\sqrt{2\left(\sqrt{x^2+y^2-x}\right)\left(\sqrt{x^2+y^2-y}\right)}\sqrt{x^2+y^2}\)
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\(=\frac{x-2\sqrt{x}+y+2\sqrt{y}-2\sqrt{xy}+1}{x-2\sqrt{xy}+y-1}\)\(=\frac{\left(\sqrt{x}-\sqrt{y}\right)^2-2\left(\sqrt{x}-\sqrt{y}\right)+1}{\left(\sqrt{x}-\sqrt{y}\right)^2-1}\)
\(=\frac{\left(\sqrt{x}-\sqrt{y}-1\right)^2}{\left(\sqrt{x}-\sqrt{y}+1\right)\left(\sqrt{x}-\sqrt{y}-1\right)}=\frac{\sqrt{x}-\sqrt{y}-1}{\sqrt{x}-\sqrt{y}+1}\)
a, ĐK: \(x,y\ge0\)
\(hpt\Leftrightarrow\left\{{}\begin{matrix}\dfrac{3\sqrt{y}}{\sqrt{x+3}-\sqrt{x}}=3\\\sqrt{x}+\sqrt{y}=x+1\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\sqrt{x}+\sqrt{y}=\sqrt{x+3}\\\sqrt{x}+\sqrt{y}=x+1\end{matrix}\right.\)
\(\Rightarrow\sqrt{x+3}=x+1\)
\(\Leftrightarrow x+3=x^2+2x+1\)
\(\Leftrightarrow\left(x-1\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-2\left(l\right)\end{matrix}\right.\)
Thay \(x=1\) vào hệ phương trình đã cho ta được \(y=1\)
Vậy pt đã cho có nghiệm \(x=y=1\)
b, \(hpt\Leftrightarrow\left\{{}\begin{matrix}\left(x+\dfrac{1}{2}\right)^2=\left(y+\dfrac{1}{2}\right)^2\\x^2+y^2=3\left(x+y\right)\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}x=y\\x+y=-1\end{matrix}\right.\\x^2+y^2=3\left(x+y\right)\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=y\\x^2-3x=0\end{matrix}\right.\left(1\right)\\\left\{{}\begin{matrix}x+y=-1\\x^2+y^2=-3\end{matrix}\right.\left(vn\right)\end{matrix}\right.\)
\(\left(1\right)\Leftrightarrow\left[{}\begin{matrix}x=y=3\\x=y=0\end{matrix}\right.\)
Vậy ...
a: \(=x-\sqrt{xy}+y-x+2\sqrt{xy}-y=\sqrt{xy}\)
b: \(=\dfrac{1+\sqrt{a}}{a-\sqrt{a}}\cdot\dfrac{\left(\sqrt{a}-1\right)^2}{\sqrt{a}+1}=\dfrac{\sqrt{a}-1}{\sqrt{a}}\)
\(ĐK:x,y\in R\)
Từ 2 PT \(\Leftrightarrow\sqrt{\left(x+1\right)^2+\left(y-1\right)^2}=\sqrt{\left(x-5\right)^2+\left(y+1\right)^2}\)
\(\Leftrightarrow x^2+2x+y^2-2y+2=x^2-10x+y^2+2y+26\\ \Leftrightarrow12x-4y-24=0\\ \Leftrightarrow3x-y-6=0\\ \Leftrightarrow y=3x-6\)
Thay vào \(PT\left(1\right)\Leftrightarrow\sqrt{\left(x-1\right)^2+\left(3x-8\right)^2}=\sqrt{\left(x+1\right)^2+\left(3x-7\right)^2}\)
\(\Leftrightarrow10x^2-50x+65=10x^2-40x+50\\ \Leftrightarrow10x=15\Leftrightarrow x=\dfrac{3}{2}\Leftrightarrow y=-\dfrac{3}{2}\)
Vậy hệ có nghiệm \(\left(x;y\right)=\left(\dfrac{3}{2};-\dfrac{3}{2}\right)\)