Question

[𝓃𝑔𝓊𝓎𝑒̂̃𝓃 𝓉𝒽𝒾̣ 𝓁𝒶𝓃 𝒶𝓃𝒽]

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Answer 1

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Bài 1: Để căn thức có nghĩa thì \(8x+2\ge0\Leftrightarrow x\ge\frac{-1}{4}\)

Bài 2: a) \(\sqrt{3}-\frac{1}{3}.\sqrt{27}+2\sqrt{507}=\sqrt{3}-\frac{1}{3}.3\sqrt{3}+2\sqrt{507}=2\sqrt{507}\)

b) \(\frac{1}{3-\sqrt{2}}=\frac{3+\sqrt{2}}{\left(3-\sqrt{2}\right)\left(3+\sqrt{2}\right)}=\frac{3+\sqrt{2}}{7}\)

c) \(5\sqrt{2}-\sqrt{\left(5\sqrt{2}-1\right)^2}=5\sqrt{2}-5\sqrt{2}+1=1\)

Answer 2

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Bài 2: \(3\sqrt{4x+20}-4\sqrt{5+x}=6\)

\(\Leftrightarrow6\sqrt{x+5}-4\sqrt{x+5}=6\)

\(\Leftrightarrow2\sqrt{x+5}=6\Leftrightarrow\sqrt{x+5}=3\)

\(\Leftrightarrow x+5=9\Leftrightarrow x=4\)

Vậy x = 4