Bài 4:
a, Để đường thẳng \(y=\left(2m-1\right)x+3\) song song với đường thẳng\(y=5x-1\)
\(\Rightarrow\left\{{}\begin{matrix}2m-1\ne5\\3\ne-1\end{matrix}\right.\Rightarrow m\ne3\)
b,\(\left\{{}\begin{matrix}2x+y=5\\3x-2y=4\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=5-2x\\3x-2\left(5-2x\right)=4\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=5-2x\\3x-10+4x=4\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=5-2x\\7x=14\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=5-2.2\\x=2\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=1\\x=2\end{matrix}\right.\)
\(\left\{{}\begin{matrix}2x+3y=7\\x+2y=4\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}2\left(4-2y\right)+3y=7\\x=4-2y\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}8-4y+3y=7\\x=4-2y\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=1\\x=4-2.1\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=1\\x=2\end{matrix}\right.\)
