Question

\(\left\{{}\begin{matrix}3x-y=5\\\\2x+3y=7\end{matrix}\right.\)

Answer 1

\(\left\{{}\begin{matrix}3x-y=5\\2x+3y=7\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}9x-3y=15\\2x+3y=7\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}11x=22\\3x-y=5\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=2\\6-y=5\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=1\end{matrix}\right.\)

Vậy...

Answer 2

3x-y=5=>  3x-5=y 

2x+3y=7

<=> 2x+3(3x-5) =7

<=>2x+9x-15=7

<=> 11x=22=>x=2

Thay x=2 vào biểu thức y=3x-5 ta có:

y=3.2-5=1