Răspuns :
[tex]\it \sigma[ABC]=\dfrac{1}{2}|\Delta|\\ \\ \\ \Delta=\begin{vmatrix} 1&-2&4\\ \\ 4&0&0\\ \\ 1&1&1\end{vmatrix}=-4\cdot \begin{vmatrix}-2&4\\ \\ 1&1 \end{vmatrix}=-4\cdot(-2-4)=24\\ \\ \\ \sigma[ABC]=\dfrac{1}{2}\cdot24=12[/tex]
[tex]\it \sigma[ABC]=\dfrac{1}{2}|\Delta|\\ \\ \\ \Delta=\begin{vmatrix} 1&-2&4\\ \\ 4&0&0\\ \\ 1&1&1\end{vmatrix}=-4\cdot \begin{vmatrix}-2&4\\ \\ 1&1 \end{vmatrix}=-4\cdot(-2-4)=24\\ \\ \\ \sigma[ABC]=\dfrac{1}{2}\cdot24=12[/tex]