I have 3 points and I want to prove that they are on the straight line the points are
$$
A(0,0,2),\quad
B(0,0,-3),\quad
C(0,0,4)
$$
To prove that they are on the straight line we need to prove that
$$
\vec AB \parallel \vec BC
$$
where
$$
\vec AB=(0,0,-5)
\quad\mbox{and}\quad
\vec BC=(0,0,7).
$$
So $\displaystyle \frac {0}{0}≠ \frac {-5}{7}$
But if we try to graph those points It seems to be they are on the straight line So please can Any one tell me what's the right.
Are they on straight line or not?!