\(x^2-11=0\\ \Leftrightarrow x^2=11\\ \Leftrightarrow\left[{}\begin{matrix}x=11\\x=-\sqrt{11}\end{matrix}\right.\)
Bài 1. \(\sqrt{0,45.100}=\sqrt{\dfrac{45}{100}.100}=\sqrt{9.5}=2\sqrt{5}\)
Bài 2. \(x^2-11=0\) ⇔ \(x^2=11\) ⇔ \(x=\sqrt{11}\) hoặc \(x=-\sqrt{11}\)
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