Question

giải bằng phương trình thế

x+2y=-2

5x-4y=11

 

Answer 1

\(\left\{{}\begin{matrix}x+2y=-2\\5x-4y=11\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-2-2y\\5\left(-2-2y\right)-4y=11\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=-2-2y\\-10-10y-4y=11\end{matrix}\right. \Leftrightarrow\left\{{}\begin{matrix}x=-2-2y\\-14y=11+10=21\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=-2-2\cdot-\dfrac{3}{2}\\y=\dfrac{21}{-14}=-\dfrac{3}{2}\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=1\\y=-\dfrac{3}{2}\end{matrix}\right.\)