F(-1)=-3x-5x^2

Solution for F(-1)=-3x-5x^2 equation:

(-1)=-3F-5F^2

We move all terms to the left:

(-1)-(-3F-5F^2)=0

We add all the numbers together, and all the variables

-(-3F-5F^2)-1=0

We get rid of parentheses

5F^2+3F-1=0

a = 5; b = 3; c = -1;
Δ = b2-4ac
Δ = 32-4·5·(-1)
Δ = 29
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{29}}{2*5}=\frac{-3-\sqrt{29}}{10}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+\sqrt{29}}{2*5}=\frac{-3+\sqrt{29}}{10}
$