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I have this equation:

$$A(f)=\frac{1}{\sqrt{\left(1-\left(\frac{f}{F}\right)^2\right)^2+c^2\left(\frac{f}{F}\right)^2}}$$

and I am told this:

Note that for a fixed amplitude $A$, the equation relating amplitude and $f$ can be converted to a 4th degree polynomial in $f$ by squaring both sides (to eliminate the square root), taking the reciprocal of both sides, and then subtracting $A$. Do this algebraic manipulation "by hand."

I got it down to a quadratic:

$$f^2 = \frac{F^4-F^4y^2}{y^2(F^2C^2-2F^2+1)}$$

Please help :)

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    Joe, I hope you don't mind, I rolled back and then incorporated your edits into my edit.2012-03-06
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    @ZevChonoles: Don't mind at all.2012-03-06
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    Somehow, when you "got it down to a quadratic," the symbol $A$ disappeared altogether. How'd you do that?2012-03-06

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