F(3)=72x^2

Solution for F(3)=72x^2 equation:

(3)=72F^2

We move all terms to the left:

(3)-(72F^2)=0

a = -72; b = 0; c = +3;
Δ = b2-4ac
Δ = 02-4·(-72)·3
Δ = 864
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{864}=\sqrt{144*6}=\sqrt{144}*\sqrt{6}=12\sqrt{6}$
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-12\sqrt{6}}{2*-72}=\frac{0-12\sqrt{6}}{-144}
=-\frac{12\sqrt{6}}{-144}
=-\frac{\sqrt{6}}{-12}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+12\sqrt{6}}{2*-72}=\frac{0+12\sqrt{6}}{-144}
=\frac{12\sqrt{6}}{-144}
=\frac{\sqrt{6}}{-12}
$