\(\text{a) ĐKXĐ: }x\ge\sqrt{3}\)
\(\sqrt{x^2-3}\le x^2-3\)
\(\Leftrightarrow\left(\sqrt{x^2-3}\right)^2\le\left(x^2-3\right)^2\)
\(\Leftrightarrow x^2-3\le x^4-6x^2+9\)
\(\Leftrightarrow x^2-3-x^4+6x^2-9\le0\)
\(\Leftrightarrow-x^4+7x^2-12\le0\)
\(\Leftrightarrow-x^2+4x^2+3x^2-12\le0\)
\(\Leftrightarrow\left(-x^4+4x^2\right)+\left(3x^2-12\right)\le0\)
\(\Leftrightarrow-x^2\left(x^2-4\right)+3\left(x^2-4\right)\le0\)
\(\Leftrightarrow\left(x^2-4\right)\left(3-x^2\right)\le0\)
\(\text{Đến đây EZ rồi}\)
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