We need to know the slope of the line m and a point (x_1,y_1).
It may seem that we do not have enough information to write our line equation. However, if we know two points we can use the Slope Formula to calculate the slope.
m = y_2-y_1/x_2-x_1
This gives us all we need to use the point-slope form, while the slope-intercept form would be harder to use since we would still not know the y-intercept.
If you are given the coordinates of two points on a line, you can use the point-slope form to find the equation of the line that passes through them.
