Question

hệ phương trình \(\left\{{}\begin{matrix}x+y=5\\x-y=1\end{matrix}\right.\)có nghiệm (x;y)là

Answer 1

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

Vậy hệ pt có nghiệm (x;y) = (3;2)

Answer 2

Ta có: \(\left\{{}\begin{matrix}x+y=5\\x-y=1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x+y=5\\x=y+1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}y+1+y=5\\x=y+1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}y=2\\x=3\end{matrix}\right.\)

Vậy...