Question

giải hệ pt 

\(\left\{{}\begin{matrix}4-2x=3y\\x+y=-3\end{matrix}\right.\)

Answer 1

\(\left\{{}\begin{matrix}2x+3y=4\\2x+2y=-6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=10\\x=-3-10=-13\end{matrix}\right.\)

Answer 2

\(\left\{{}\begin{matrix}4-2x=3y\\x+y=-3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x+3y=4\\x+y=-3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}2x+3y=4\\2x+2y=-6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=10\\x+y=-3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=10\\x=-7\end{matrix}\right.\)

Answer 3

\(\Leftrightarrow\left\{{}\begin{matrix}-2x-3y=-4\\x+y=-3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-2x-3y=-4\\2x+2y=-6\end{matrix}\right.\)

cộng từng vế của 2 pt ta có:

\(\Leftrightarrow-y=-10\)

\(\Leftrightarrow y=10\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=10\\x+y=-3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=10\\x+10=-3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=10\\x=-13\end{matrix}\right.\)