a)
\(\left\{{}\begin{matrix}4x+5y=3\\x-3y=5\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}4x+5y=3\\4x-12y=20\end{matrix}\right.\\ \Leftrightarrow17y=-17\Leftrightarrow y=-1\Leftrightarrow x=5+3.\left(-1\right)=2\)
b)
\(\left\{{}\begin{matrix}7x-2y=1\\3x+y=6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}7x-2y=1\\6x+2y=12\end{matrix}\right.\\ \Leftrightarrow13x=13\Leftrightarrow x=1\Leftrightarrow y=\dfrac{7.1-1}{2}=3\)
Còn c, d cứ làm tương tự nha
a: \(\left\{{}\begin{matrix}4x+5y=3\\x-3y=5\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}4x+5y=3\\4x-12y=20\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}17y=-17\\x-3y=5\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}y=-1\\x=3y+5=3\cdot\left(-1\right)+5=2\end{matrix}\right.\)
b: \(\left\{{}\begin{matrix}7x-2y=1\\3x+y=6\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}7x-2y=1\\6x+2y=12\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}13x=13\\3x+y=6\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x=1\\y=6-3x=6-3\cdot1=3\end{matrix}\right.\)
c: \(\left\{{}\begin{matrix}x+2y=5\\4x-7y=1\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}4x+8y=20\\4x-7y=1\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}15y=19\\x+2y=5\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}y=\dfrac{19}{15}\\x=5-2y=5-\dfrac{38}{15}=\dfrac{37}{15}\end{matrix}\right.\)
d: \(\left\{{}\begin{matrix}4x-5y=3\\x+3y=-5\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}4x-5y=3\\4x+12y=-20\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-17y=23\\x+3y=-5\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}y=-\dfrac{23}{17}\\x=-5-3y=-5-3\cdot\dfrac{-23}{17}=-5+\dfrac{69}{17}=-\dfrac{16}{17}\end{matrix}\right.\)
