F(x)=100-4x^2

Solution for F(x)=100-4x^2 equation:

(F)=100-4F^2

We move all terms to the left:

(F)-(100-4F^2)=0

We get rid of parentheses

4F^2+F-100=0

a = 4; b = 1; c = -100;
Δ = b2-4ac
Δ = 12-4·4·(-100)
Δ = 1601
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-\sqrt{1601}}{2*4}=\frac{-1-\sqrt{1601}}{8}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{1601}}{2*4}=\frac{-1+\sqrt{1601}}{8}
$