c)
ĐKXĐ: \(x\notin\left\{2;-2\right\}\)
Ta có: \(\dfrac{2\left(11-x\right)}{4-x^2}=\dfrac{x-2}{x+2}-\dfrac{3}{x-2}\)
\(\Leftrightarrow\dfrac{\left(x-2\right)^2}{\left(x+2\right)\left(x-2\right)}-\dfrac{3\left(x+2\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{2\left(x-11\right)}{x^2-4}\)
Suy ra: \(x^2-4x+4-3x-6-2x+22=0\)
\(\Leftrightarrow x^2-9x+20=0\)
\(\Leftrightarrow\left(x-5\right)\left(x-4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5\left(nhận\right)\\x=4\left(nhận\right)\end{matrix}\right.\)
Vậy: S={5;4}
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