Math Forum / Mathematics / Undergraduate Math

Years ago I noted that with math people I was stuck unable to convince
them with mathematical proof, which doesn't quite make sense, and it
puzzled me for years, and of course on Usenet posters claimed
otherwise (I found it to be true off Usenet as well, for instance with

I've been curious for years about hostile reactions to my postings,
and for lots of reasons, including in the past worrying that posters
were working to block widespread acceptance of my research, which is a
concern which has faded.  It's not that I don't think negative claims

One of the things that gets posters who argue with me more hot and
bothered than anything else is this notion that I'm trying to get
famous.  I'm not.  In fact, it's quite dangerous to get famous.  Or to
be a celebrity which is not necessarily famous in my opinion but is

There is a lot of satisfaction with having my own axiom, which I had
the honor of naming as I'm the discoverer, which is of course, the
prime residue axiom, and yes, posters can reply in the negative or
derisively, but there you see the difference between finding something

Having trouble in evaluate the limit of ( (2(x^2-8))^1/2 ) + x) / (x+4), as x approaches -4. Hints please?  
I think that I need use some variable substitution... But I try x^2 = t but not work, in really I don't understand how variable substitution working in limits.
thanks a lot