How to find if the points fall in a straight line or not? Three points $(x_1,y_1), (x_2,y_2)$ and $(x_3,y_3)$ whether fall in a straight line or not. How do I do that?

Another way: a certain cross product must be zero, or
$$ \left( (x_2-x_1)\hat{i}+(y_2-y_1)\hat{j}\right) \times \left((x_3-x_1) \hat{i}+(y_3-y_1)\hat{j}\right)=\vec{0}$$
$$\implies (x_2-x_1)(y_3-y_1)-(y_2-y_1)(x_3-x_1) = 0$$
