Question:
The following system of linear equations
$3 x+3 y+2 z=9$
$3 x+2 y+2 z=9$
$x-y+4 z=8$
Correct Option: , 2
Solution:
$\Delta=\left|\begin{array}{ccc}2 & 3 & 2 \\ 3 & 2 & 2 \\ 1 & -1 & 4\end{array}\right|=-20 \neq 0 \quad \therefore$ unique solution
$\Delta_{x}=\left|\begin{array}{ccc}9 & 3 & 2 \\ 9 & 2 & 2 \\ 8 & -1 & 4\end{array}\right|=0$
$\Delta_{y}=\left|\begin{array}{lll}2 & 9 & 2 \\ 3 & 9 & 2 \\ 1 & 8 & 4\end{array}\right|=-20$
$\left|\begin{array}{ccc}2 & 3 & 9 \\ 3 & 2 & 9 \\ 1 & -1 & 8\end{array}\right|=-40$
$\therefore \quad x=\frac{\Delta_{\mathrm{X}}}{\Delta}=0$
$y=\frac{\Delta_{y}}{\Delta}=1$
$z=\frac{\Delta_{x}}{\Delta}=2$
Unique solution: $(0,1,2)$