F(x)=x2-4x-8

Solution for F(x)=x2-4x-8 equation:

(F)=F2-4F-8

We move all terms to the left:

(F)-(F2-4F-8)=0

We add all the numbers together, and all the variables

-(+F^2-4F-8)+F=0

We get rid of parentheses

-F^2+4F+F+8=0

We add all the numbers together, and all the variables

-1F^2+5F+8=0

a = -1; b = 5; c = +8;
Δ = b2-4ac
Δ = 52-4·(-1)·8
Δ = 57
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{57}}{2*-1}=\frac{-5-\sqrt{57}}{-2}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+\sqrt{57}}{2*-1}=\frac{-5+\sqrt{57}}{-2}
$