# Second Derivative in Terms of Y

1. Sep 14, 2011

### whoopie88

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. Sep 14, 2011

### HallsofIvy

Staff Emeritus
You can't. The problem you give makes no sense. If you have an equation like $4x^2+ 3x- 9y^2= 0$ 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 $f(x,y)= 4x^2+ 3x- 9y^2$ 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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