Stelsels

Werk uit

\(\left\{\begin{matrix}3y+3x=-12\\-3x-10y=-9\end{matrix}\right.\)

\(\left\{\begin{matrix}3y+3x=-12\\-3x-10y=-9\end{matrix}\right.\\ \Leftrightarrow \left\{\begin{matrix}3x+3y=-12\\-3x-10y=-9\end{matrix}\right.\text{(Niet verplichte stap, proper schrijven)}\\ \Leftrightarrow \left\{\begin{array}{c|c|c}3x+3y=-12& \color{red}{1.} & \color{blue}{10.} \\-3x-10y=-9& \color{red}{1.} & \color{blue}{3.} \end{array}\right.\\ \Leftrightarrow \left\{\begin{matrix} \color{red}{\underline{3x-3x}+3y-10y=-12-9} \\ \color{blue}{30x-9x\underline{+30y-30y}=-120-27} \end{matrix}\right.\\ \Leftrightarrow \left\{\begin{matrix}-7y=-21 \\21x=-147\end{matrix}\right.\\ \Leftrightarrow \left\{\begin{matrix}y=\frac{-21}{-7}=3 \\x=\frac{-147}{21}=-7\end{matrix}\right.\\ \qquad V=\{(-7,3)\}\)