a.
\(x^2-2\sqrt{13}x+13=0\)
\(\Leftrightarrow\left(x-\sqrt{13}\right)^2=0\)
\(\Leftrightarrow x-\sqrt{13}=0\)
\(\Leftrightarrow x=\sqrt{13}\)
b.
\(\sqrt{x^2-10x+25}=7-2x\)
\(\Leftrightarrow\sqrt{\left(x-5\right)^2}=7-2x\)
\(\Leftrightarrow\left|x-5\right|=7-2x\)
\(\Leftrightarrow\left\{{}\begin{matrix}7-2x\ge0\\\left[{}\begin{matrix}x-5=7-2x\\5-x=7-2x\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\le\dfrac{7}{2}\\\left[{}\begin{matrix}x=4\left(loai\right)\\x=2\end{matrix}\right.\end{matrix}\right.\)
\(\Rightarrow x=2\)
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