TH1: x>=0
Hệ phương trình sẽ trở thành:
\(\left\{{}\begin{matrix}2x-5-y=0\\5x+3y=18\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}2x-y=5\\5x+3y=18\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}6x-3y=15\\5x+3y=18\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}11x=33\\5x+3y=18\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=3\left(nhận\right)\\y=\dfrac{18-5x}{3}=\dfrac{18-5\cdot3}{3}=1\end{matrix}\right.\)
TH2: x<0
Hệ phương trình sẽ trở thành:
\(\left\{{}\begin{matrix}-2x-5-y=0\\5x+3y=18\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}-2x-y=5\\5x+3y=18\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}-6x-3y=15\\5x+3y=18\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-x=33\\-2x-y=5\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x=-33\left(nhận\right)\\y=-2x-5=-2\cdot\left(-33\right)-5=66-5=61\end{matrix}\right.\)
