F(x)=-0.07x^2+3.5x

Solution for F(x)=-0.07x^2+3.5x equation:

(F)=-0.07F^2+3.5F

We move all terms to the left:

(F)-(-0.07F^2+3.5F)=0

We get rid of parentheses

0.07F^2-3.5F+F=0

We add all the numbers together, and all the variables

0.07F^2-2.5F=0

a = 0.07; b = -2.5; c = 0;
Δ = b2-4ac
Δ = -2.52-4·0.07·0
Δ = 6.25
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{-(-2.5)-\sqrt{6.25}}{2*0.07}=\frac{2.5-\sqrt{6.25}}{0.14}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2.5)+\sqrt{6.25}}{2*0.07}=\frac{2.5+\sqrt{6.25}}{0.14}
$