F(-3)=-3x^2-8x-7

Solution for F(-3)=-3x^2-8x-7 equation:

(-3)=-3F^2-8F-7

We move all terms to the left:

(-3)-(-3F^2-8F-7)=0

We add all the numbers together, and all the variables

-(-3F^2-8F-7)-3=0

We get rid of parentheses

3F^2+8F+7-3=0

We add all the numbers together, and all the variables

3F^2+8F+4=0

a = 3; b = 8; c = +4;
Δ = b2-4ac
Δ = 82-4·3·4
Δ = 16
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{16}=4$
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-4}{2*3}=\frac{-12}{6}
=-2
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+4}{2*3}=\frac{-4}{6}
=-2/3
$