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Homework Help: Second Derivative in Terms of Y

  1. Sep 14, 2011 #1
    1. The problem statement, all variables and given/known data
    Find the second derivative of 4x^2 + 3x - 9y^2. Answer in terms of y.


    2. Relevant equations
    All derivative formulas.

    3. The attempt at a solution
    [PLAIN]http://http://i52.tinypic.com/2w2ptex.jpg [Broken]

    I can't get much further than this; the thing that gets me is how to put everything in terms of y. Help? Thanks!
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Sep 14, 2011 #2

    HallsofIvy

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    Science Advisor

    You can't. The problem you give makes no sense. If you have an equation like [itex]4x^2+ 3x- 9y^2= 0[/itex] then y is defined as an "implicit" function of x and you can find the first and second derivatives of y with respect to x.

    Or, if you have a function [itex]f(x,y)= 4x^2+ 3x- 9y^2[/itex] you can find the the second derivative of f with respect to y.

    Please check and tell us what the problem really is.
     
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