Question

Answer 1

giải pt bằng phương pháp thế 

Answer 2

\(a,\Leftrightarrow\left\{{}\begin{matrix}18-4y-3y=-3\\x=9-2y\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=9-2y\\7y-18=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=3\\y=3\end{matrix}\right.\\ b,\Leftrightarrow\left\{{}\begin{matrix}x=y+1\\2y+2+3y=38\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=y+1\\5y=36\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{41}{5}\\y=\dfrac{36}{5}\end{matrix}\right.\\ c,\Leftrightarrow\left\{{}\begin{matrix}x=-y-2\\-2y-4-y=-13\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-y-2\\-3y=-9\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-5\\y=3\end{matrix}\right.\)