Question
Find the vector equation of the line through the origin which is perpendicular to the plane
Solution
The equation of plane is 
∴ direction-ratios of the normal are 1,–2, 1
Also normal passes through origin (0, 0, 0)
∴ vector equation of line is

or

∴ direction-ratios of the normal are 1,–2, 1
Also normal passes through origin (0, 0, 0)
∴ vector equation of line is

or
