F(x)=0.7x^2-2.8x

Solution for F(x)=0.7x^2-2.8x equation:

(F)=0.7F^2-2.8F

We move all terms to the left:

(F)-(0.7F^2-2.8F)=0

We get rid of parentheses

-0.7F^2+F+2.8F=0

We add all the numbers together, and all the variables

-0.7F^2+3.8F=0

a = -0.7; b = 3.8; c = 0;
Δ = b2-4ac
Δ = 3.82-4·(-0.7)·0
Δ = 14.44
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{-(3.8)-\sqrt{14.44}}{2*-0.7}=\frac{-3.8-\sqrt{14.44}}{-1.4}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3.8)+\sqrt{14.44}}{2*-0.7}=\frac{-3.8+\sqrt{14.44}}{-1.4}
$