a)
\(\left\{{}\begin{matrix}\dfrac{1}{x+y}-\dfrac{2}{x-y}=2\\\dfrac{5}{x+y}-\dfrac{4}{x-y}=3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}\dfrac{2}{x+y}-\dfrac{4}{x-y}=4\\\dfrac{5}{x+y}-\dfrac{4}{x-y}=3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}\dfrac{3}{x+y}=-1\\\dfrac{1}{x+y}-\dfrac{2}{x-y}=2\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x+y=-3\\-\dfrac{1}{3}-\dfrac{2}{x-y}=2\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x+y=-3\\\dfrac{2}{x-y}=-\dfrac{7}{3}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x+y=-3\\x-y=-\dfrac{7}{6}\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}2x=-\dfrac{16}{3}\\x+y=-3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{8}{3}\\y=-3+\dfrac{8}{3}=-\dfrac{1}{3}\end{matrix}\right.\)
