go to http://hyperphysics.phy-astr.gsu.edu/hbase/alg2.html#ap

 

scroll down to the part on algebra practice equations.

 

x = (b(e-c))/(a-bd)

 

so a can't = bd or the equation becomes undefined.

 

put x + 0 = x + 0 and you get NaN. what's NaN? Does that mean all real numbers?

 

put x + 1 = x + 0 and you get -Infinity... I don't get it. I thought it was null set.

 

put x + 0 = x + 1 and you get Infinity... I don't get that either. I thought it was null set.

All that system is doing is taking the coefficients and placing them into the equation for x just above. Some coefficients make the unique solution impossible to find.

 

NaN stands for Not a Number, it is the way computers generally say "undefined". It comes about since the system tries to find the unique result of 0/0. The system isn't designed to handle sets at all, so in this case you could interpret NaN to mean "the set of all real numbers", or "I don't have enough info to be able to tell", etc.

 

You get infinity since it tries to calculate 1/0. You get -infinity since it tries to calculate -1/0. You are right in thinking it is a null set, but computers don't think like that.

Thanks, that makes sense now.

In short: don't trust everything your calculator tells you