F(-4)=3x-5x^2

Solution for F(-4)=3x-5x^2 equation:

(-4)=3F-5F^2

We move all terms to the left:

(-4)-(3F-5F^2)=0

We add all the numbers together, and all the variables

-(3F-5F^2)-4=0

We get rid of parentheses

5F^2-3F-4=0

a = 5; b = -3; c = -4;
Δ = b2-4ac
Δ = -32-4·5·(-4)
Δ = 89
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)-\sqrt{89}}{2*5}=\frac{3-\sqrt{89}}{10}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+\sqrt{89}}{2*5}=\frac{3+\sqrt{89}}{10}
$