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 :)