Question

Determine a equação reta que passa pelos pontos A e B em cada caso.

- A = (1, - 4) e B (2 , -8)

Answer 1

$\begin{vmatrix}\sf1&\sf-4&\sf1\\\sf2&\sf-8&\sf1\\\sf x&\sf y&\sf1\end{vmatrix}=0$

$\sf 1\cdot(-8-y)+4(2-x)+1\cdot(2y+8x)=0\\\sf -\diagdown\!\!\!\!8-y+\diagdown\!\!\!\!8-4x+2y+8x=0\\\huge\boxed{\boxed{\boxed{\boxed{\sf y+4x=0}}}}\blue{\checkmark}$