Let's write the parametric line
(x,y,z) = (0,2,8) + t(5,-1,4)
(5,-1,4) is called the direction vector of the line. It's normal to the plane
5x - y + 4z = constant
We get the constant by substituting the point (3,0,7),
5x - y +4z = 5(3) - 0 + 4(7) = 43
5x - y +4z = 43
