a)\(\dfrac{2}{x^2-1}+\dfrac{1}{x+1}=2\) Điều kiện:x#1,-1
\(\Leftrightarrow\dfrac{2}{\left(x+1\right)\left(x-1\right)}+\dfrac{1}{x+1}=2\\\)
\(\Leftrightarrow\dfrac{2+x-1}{\left(x+1\right)\left(x-1\right)}=2\)
\(\Leftrightarrow\dfrac{1}{x-1}=2\)
\(\Leftrightarrow1=2\left(x-1\right)\)
\(\Leftrightarrow2x=3\)
\(\Leftrightarrow x=\dfrac{3}{2}\)
b)\(1-\dfrac{12}{x^2-4}=\dfrac{3}{x+2}\) Điều kiện:x#2,-2
\(\Leftrightarrow\dfrac{x^2-4-12}{x^2-4}=\dfrac{3}{x+2}\)
\(\Leftrightarrow x^2-16=3\left(x-2\right)\)
\(\Leftrightarrow x^2-16-3x+6=0\)
\(\Leftrightarrow x^2-3x-10=0\)
\(\Leftrightarrow\left(x-5\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-5=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=-2\end{matrix}\right.\)
Vậy \(S=\left\{5\right\}\)
