My Math Forum Help plz with VERY beginner limits.

 Calculus Calculus Math Forum

 July 26th, 2010, 04:26 PM #1 Newbie   Joined: Sep 2009 Posts: 18 Thanks: 0 Help plz with VERY beginner limits. I suck at even the easiest of calculus that I'm trying to learn. Like this easy question that I can't figure out. limit (x-2) / (x^2-x-2) x -> 2 I found the limit to be .33, but I don't think that's right. ******** Does limits always have to go to a whole number? Thanks!
July 26th, 2010, 04:31 PM   #2
Senior Member

Joined: Feb 2009

Posts: 1,519
Thanks: 3

Re: Help plz with VERY beginner limits.

That's correct. The limit is 1/3.

Quote:
 Do limits always have to go to a whole number?
No. Who told you that???

 July 26th, 2010, 04:33 PM #3 Global Moderator     Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,807 Thanks: 1045 Math Focus: Elementary mathematics and beyond Re: Help plz with VERY beginner limits. If by .33 you mean 1/3 then you are correct. $\lim_{x \to 2}\,\frac{x\,-\,2}{x^2\,-\,x\,-2}\,=\,\lim_{x \to 2}\,\frac{x\,-\,2}{(x\,-\,2)(x\,+\,1)}$ $=\,\lim_{x \to 2}\,\frac{1}{x\,+\,1}\,=\,\frac{1}{3}$
 July 26th, 2010, 05:08 PM #4 Newbie   Joined: Sep 2009 Posts: 18 Thanks: 0 Re: Help plz with VERY beginner limits. Thanks. I think this makes sense now. I have like 50 more practice questions so I'm sure I'm going to get confused again. Thanks again for helping
 July 26th, 2010, 05:55 PM #5 Newbie   Joined: Sep 2009 Posts: 18 Thanks: 0 Re: Help plz with VERY beginner limits. Oh and I have another question. Can all limits be put into a fraction such as 1/3, 1/4, 1/8, etc. Are there such thing as a limit like: 0.2352354364564636346465745634523536577436345 where it can't be put into a fraction?
 July 26th, 2010, 06:09 PM #6 Global Moderator     Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,807 Thanks: 1045 Math Focus: Elementary mathematics and beyond Re: Help plz with VERY beginner limits. $\lim_{x \to 2}\,\sqrt{x}\,=\,\sqrt{2},$ which is irrational, i.e. it can't be expressed as a fraction. A limit may evaluate to any real number: a fraction, an integer, an irrational number and so on.
 August 1st, 2010, 02:13 PM #7 Newbie   Joined: Sep 2009 From: Greece Posts: 12 Thanks: 0 Math Focus: Calculus Re: Help plz with VERY beginner limits. Factorizing made by greg1313, is the way which must always be checked first, but you can try L'Hospital's rule right from the beginning and this is very quick too: because if you calculate lim for x->2 you have $\frac{0}{0}$ form, you use L'Hospital's rule:$\lim_{x \to \2} \frac{x-2}{x^{2}-x-2}=\lim_{x \to \2} \frac{1}{2x-1}=\frac{1}{3}$ (taking the first derivatives of both numerator and denominator).Hope this is helpful too.
 August 1st, 2010, 05:17 PM #8 Global Moderator     Joined: Nov 2009 From: Northwest Arkansas Posts: 2,766 Thanks: 4 Re: Help plz with VERY beginner limits. Here's a quick "order of operations" (if you will, but I'm sure many won't!) for algebraic limits. I assume you don't know about the hospital rule (yet)... 1. Direct substitution. If plugging in the value of x to which x approaches (call it "c") doesn't give you something crazy/undefined, then you're done. 2. Factor/polynomial long division. If you can cancel a factor of (x - c), you should be ready to use direct sub. 3. Conjugates. If you have a +/- sqrt(b) in the denominator, multiply the fraction by its conjugate (a -/+ sqrt(b)) and that should clear things up. There are some tricks for evaluating trig limits, but we'll cross that bridge/bump that thread at a later date!

 Tags beginner, limits, plz

 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post shunya Computer Science 3 November 27th, 2013 09:54 AM Peter1107 Calculus 6 August 2nd, 2011 09:23 AM phss Calculus 2 January 19th, 2011 10:08 AM prathimarao Algebra 7 June 10th, 2009 08:26 PM Mark Computer Science 2 October 30th, 2007 02:32 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top