Theory
A vector describes a movement. It has size and direction.
A column vector has two numbers. The top number is horizontal movement and the bottom number is vertical movement.
Positive horizontal movement is right and negative horizontal movement is left. Positive vertical movement is up and negative vertical movement is down.
To add vectors, add the horizontal components and add the vertical components.
To subtract vectors, subtract the components in the same positions.
Multiplying a vector by a scalar changes its length. If the scalar is negative, the vector points in the opposite direction.
Two vectors are parallel if one is a multiple of the other, for example [6, -4] = 2[3, -2].
In geometry questions, follow the route carefully. If AB is vector a and BC is vector b, then AC = a + b.