Question

Giải pt bằng phương pháp thế {x+3y=-4 {5x-8y=3

Answer 1

\(\left\{{}\begin{matrix}x+3y=-4\\5x-8y=3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=-4-3y\\5\left(-4-3y\right)-8y=3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=-4-3y\\-20-15y-8y=3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=-4-3y\\-20-23y=3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=-4-3\left(-1\right)\\y=-1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=-1\\y=-1\end{matrix}\right.\)