just remember [2]+[2]=[1] and we’re all set

pp. 2 & 3 of the newly-minted .

the (linear) equations above the line
will turn out to correspond to “finite points”
of the projective space of the title;
the algebraically-alert will easily confirm
that these are the lines (in )
having “finite slopes”. the x = A
lines can then be thought of as
having *infinite* slope (and represented,
just as in R^2 [ordinary real 2-space],
by *vertical* lines). here come the
next couple pages.

(the icon by my finger, for now,
indicates only that these three
latest points “have something
in common”… a hint of things
to come.)