we can nest
HOWEVER, only 7 deep
restriction of Excel


this is limitation
the other is that the formula becomes incredibly complicated

we can reduce the height of the tree by BALANCING the tree
then we can ask a lot more questions
and get a lot more results
specifically, 2^height results

AI = artificial intelligence
expert system
20Q

2^20?

Turing Test. by Alan Turing
http://en.wikipedia.org/wiki/Alan_Turing

http://www.sosmath.com/CBB/viewtopic.php?t=7238&sid=e7a5ec278f2f205c20b1b11074468e35

chatbots
eliza
http://www.cleverbot.com/

try interacting with one of these
=RATE(5,-4500,-25000,70000,0)
=NPER(0.6%, -1000, 12000, 1000000, 0)
=A2/12
=PV(0.7%, 10*12, -1000, 1000000, 0)
=PV(8%, 25, 25000, 0, 0)
forever?
=PV(8%, 3000, 25000, 0, 0)

=PV(8%, 1000, 0, 1000000)