infinity minus infinity is not undefined,it is indeterminate.more specifically,it is what we mathematicians call an indeterminate form.indeterminate is very much different from undefined.undefined means we cannot assign any real number to be the answer.on the other hand,indeterminate means the answer may still be any number;we just are not sure yet.

consider the following:the expression x+1 blows up to infinity as x goes to infinity.the expression x+2 blows up to infinity as well if we let x go to infinity.therefore,the expression (x+2)-(x+1) represents infinity minus infinity as x approaches infinity.but here,we know that (x+2)-(x+1)=1,so here,even if x approaches infinity,infinity minus infinity is equal to 1.

next,consider the following two expressions x+1 and x+3.again,both blow up to infinity as x approaches infinity.so (x+3)-(x+1) represents infinity minus infinity again.but now,infinity minus infinity is 2.

another!how about 2x+1 and x+1?again,both approach infinity as x approaches infinity,so this is also infinity minus infinity.but (2x+1)-(x+1) is x,so here,infinity minus infinity is infinity!zomgwtfbbq!

to put it simply,indeterminate means the answer cannot be determined yet.as i tell my students,indeterminate means we are not yet done.

Quote Originally Posted by Raistlin
Math is fun, not boring.
i absolutely (not conditionally I cried aloud with mirth and merriment) agree.i cant say much about other people though.