\(x^2+y^2-2x+4y+5=0\)
\(\Rightarrow x^2+y^2-2x+4y+1+4=0\)
\(\Rightarrow\left(x^2-2x+1^2\right)+\left(y^2+4y+2^2\right)=0\)
\(\Rightarrow\left(x-1\right)^2+\left(y+2\right)^2=0\)
Vì : \(\left(x-1\right)^2\ge0\forall x\)
\(\left(y+2\right)^2\ge0\forall y\)
\(\Rightarrow\left(x-1\right)^2+\left(y+x\right)^2=0\)
\(\Leftrightarrow\begin{cases}\left(x-1\right)^2=0\\\left(y+2\right)^2=0\end{cases}\Rightarrow\begin{cases}x-1=0\\y+2=0\end{cases}\Rightarrow}\begin{cases}x=1\\y=-2\end{cases}}\)
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