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Math Help - Curve Sketching stuck

  1. #1
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    Lightbulb Curve Sketching stuck

    Hi,
    Stuck on curve sketching on the following.
    y = x^5 -5x

    You have part A which is finding the x-intercepts when y=0. I found x=0 and x= +and- 1.495.
    IS THIS CORRECT??? please check

    Then Part b is min/max when y'=0
    y'=5x^4-5

    5(x^4-1)=0
    5=0 CANT USE........... then X= ROOT of 1 comes to x= - or + 1????
    Then to solve for Y it s x= 1,-4 and x= -1,4 ???


    Part C is pts of inflection y''=0
    So it's y"=20x^3
    How to solve for X???

    Can some one direct me in the right direction, thanks
    Joanne
    Last edited by bradycat; March 8th 2011 at 03:37 PM.
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  2. #2
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    Quote Originally Posted by bradycat View Post
    Then Part b is min/max when y'=0
    y'=5x^4-5
    \displaystyle y'=0

    \displaystyle 5x^4-5=0

    \displaystyle 5x^4=5

    \displaystyle x^4=\frac{5}{5}

    \displaystyle x^4=1

    \displaystyle x=\sqrt[4]{1} = \pm1
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  3. #3
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    I got it, thanks.
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