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!

Trouble taking a derivative

  1. Oct 17, 2012 #1
    1. The problem statement, all variables and given/known data
    Derivative of [tex]\frac{y - 1}{y^2 - y + 1}[/tex]

    2. Relevant equations

    3. The attempt at a solution

    The solution is [tex]\frac{y^2 - 2y}{(y^2 - y + 1)^2}[/tex] but in my work, the answer will have something to the 4th power on the top which will be impossible to cancel out. What have I done wrong?

    Edit: Never mind, I see my mistake
    Last edited: Oct 17, 2012
  2. jcsd
  3. Oct 17, 2012 #2
    Remember: [tex]\frac{d}{dx}\frac{f(x)}{g(x)} = \frac{g(x)f'(x) - f(x)g'(x)}{g(x)^2}[/tex]
  4. Oct 17, 2012 #3
    Yes but I don't like to work with the quotient rule. I should be getting the same answer using the product rule anyway, right?

    Edit: Never mind, I see my mistake
  5. Oct 17, 2012 #4
    That's fine.

    Then, remember: [tex]-(y^2-y+1)^{-2} = -\frac{1}{(y^2-y+1)^2}[/tex]
    (An expression to the -2 power doesn't equal 1/sqrt(expression))
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook