a: \(\Leftrightarrow\left\{{}\begin{matrix}35x-28y=21\\35x-45y=40\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=-\dfrac{19}{17}\\x=-\dfrac{5}{17}\end{matrix}\right.\)
\(a,\Leftrightarrow\left\{{}\begin{matrix}35x-28y=21\\35x-45y=40\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}5x-4y=3\\17y=-19\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{5}{17}\\y=-\dfrac{19}{17}\end{matrix}\right.\)
\(b,\Leftrightarrow\left\{{}\begin{matrix}2x+4\sqrt{2}y=\sqrt{2}\\2x+4\sqrt{2}y=5\end{matrix}\right.\Leftrightarrow x,y\in\varnothing\)
