Question

GIẢI PP THẾ 

a) 3x-y=3

     2x+y=7

b) 3x-y=5

     2y-x=0

Answer 1

a)

\(\left\{{}\begin{matrix}3x-y=3\\2x+y=7\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=3x-3\\2x+y=7\end{matrix}\right.\\ \Leftrightarrow2x+3x-3=7\\ \Leftrightarrow5x-3=7\\ \Leftrightarrow5x=10\\ \Leftrightarrow x=2\\ \Leftrightarrow y=3.2-3=6-3=3\)

Vậy \(S=\left\{x;y\right\}=\left\{2;3\right\}\)

b)

\(\left\{{}\begin{matrix}3x-y=5\\2y-x=0\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}3x-y=5\\x=2y\end{matrix}\right.\\ \Leftrightarrow3.2y-y=5\\ \Leftrightarrow5y=5\\ \Leftrightarrow y=1\\ \Leftrightarrow x=2y=2.1=2\)

Vậy \(S=\left\{x;y\right\}=\left\{1;2\right\}\)