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

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

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

We move all terms to the left:

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

We add all the numbers together, and all the variables

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

We get rid of parentheses

3F^2-5F-4=0

a = 3; b = -5; c = -4;
Δ = b2-4ac
Δ = -52-4·3·(-4)
Δ = 73
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{-(-5)-\sqrt{73}}{2*3}=\frac{5-\sqrt{73}}{6}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+\sqrt{73}}{2*3}=\frac{5+\sqrt{73}}{6}
$