Solution to Exercise 3.9.
Geometry is the only science that it hath pleased God hitherto to bestow on mankind.
—Thomas Hobbes (1588–1679)

Exercise 3.9.  
(a)  What are the coordinates of the origin?

       The coordinates of the origin are (0, 0, 1).

(b)  Find the general form of a line l[l₁ , l₂, l₃] through the origin.

       Since the origin satisfies the equation of the line,  Hence l₃  = 0. Therefore, the general form for a line through the origin is [l₁ , l₂, 0].