1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Where did the negative go?

  1. Sep 28, 2012 #1
    http://math.colorado.edu/~jkeller/math1300/lectures/L8limits3.pdf [Broken]

    Example 8, the 2nd to 3rd step... where did the negative go? It's (x^2 - 3x) - x^2 then it became 3x in the numerator. Where'd the negative go? I don't see any other sign changes so could someone please tell me?
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Sep 28, 2012 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    It looks like an error: the minus sign should not have gone away. Intuitively, you can see the answer must be <= 0 because sqrt(x^2 - 3x) < x for x > 0, so when we subtract x we get a negative result. That does not allow for a positive limit.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook