ĐK: x \(\ge11\)
\(\sqrt{x+\sqrt{x-11}}+\sqrt{x-\sqrt{x-11}}=4\Leftrightarrow2x+2\sqrt{x^2-x+11}=16\Leftrightarrow\sqrt{x^2-x+11}=8-x\) ( x \(\le8\) ) \(\Leftrightarrow x^2-x+11=\left(8-x\right)^2\Leftrightarrow x^2-x+11=64-16x+x^2\Leftrightarrow15x-53=0\Leftrightarrow x=\dfrac{53}{15}\) (ktmđk)
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