F(x)=-3.5x^2

Solution for F(x)=-3.5x^2 equation:

(F)=-3.5F^2

We move all terms to the left:

(F)-(-3.5F^2)=0

We get rid of parentheses

3.5F^2+F=0

a = 3.5; b = 1; c = 0;
Δ = b2-4ac
Δ = 12-4·3.5·0
Δ = 1
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1}=1$
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-1}{2*3.5}=\frac{-2}{7}
=-2/7
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+1}{2*3.5}=\frac{0}{7}
=0
$