Question

Os pontos A (x;3) B (-2;5) C (-1;3) são colineares.Qual valor de X?

Answer 1

$\begin{bmatrix}x&3&1\\-2&5&1\\-1&3&1\end{bmatrix}=0$

$x\begin{bmatrix}5&1\\3&1\end{bmatrix}-3\begin{bmatrix} -2&1\\-1&1\end{bmatrix}+1\begin{bmatrix}-2&5\\-2&3\end{bmatrix} \\=0$

$x(5-3)-3(-2+1)+1(-6+5)=0$

$2x+3-1=0\\2x+2=0\\2x=-2$

$\it{x=-\dfrac{2}{2}}$

$\boxed{\boxed{\it{x=-1}}}$