we have that
The line passes through the points 

If the point passes through the origin
then 
The linear equation is a direct variation
Remember that
A relationship between two variables, x, and y, represent a direct variation if it can be expressed in the form 
 or
 or 

In this case the constant of proportionality k is equal to the slope of the line
Find the value of k

Substitute the values of x and y of the point B


the equation of the line is

therefore
the answer is
