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

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

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

We move all terms to the left:

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

We add all the numbers together, and all the variables

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

-3F^2+5F+2=0

a = -3; b = 5; c = +2;
Δ = b2-4ac
Δ = 52-4·(-3)·2
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-7}{2*-3}=\frac{-12}{-6}
=+2
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+7}{2*-3}=\frac{2}{-6}
=-1/3
$