Question

$\left[\begin{array}{ccc}1&x&2\\x&x&-1\\x&x&3\end{array}\right]= 0 \\ \\ A) 0 e 1 \\ B) 0 \\ C) 1 \\ D) 1 e 2 \\ E) 0 e 2$

Answer 1

$\left[\begin{array}{ccc}1&x&2\\x&x&-1\\x&x&3\end{array}\right]\left[\begin{array}{ccc}1&x\\x&x\\x&x\end{array}\right]$

$3x-x^2+2x^2-2x^2+x-3x^2=0$

$-4x^2+4x=0$

$4x^2-4x=0$

$4x\cdot(x-1)=0$

$\bullet 4x=0 \iff \boxed{x=0}$

$\bullet x-1=0 \iff \boxed{x=1}$

$\texttt{Alternativa A}$