F(x)=x2-8x+20

Solution for F(x)=x2-8x+20 equation:

(F)=F2-8F+20

We move all terms to the left:

(F)-(F2-8F+20)=0

We add all the numbers together, and all the variables

-(+F^2-8F+20)+F=0

We get rid of parentheses

-F^2+8F+F-20=0

We add all the numbers together, and all the variables

-1F^2+9F-20=0

a = -1; b = 9; c = -20;
Δ = b2-4ac
Δ = 92-4·(-1)·(-20)
Δ = 1
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1}=1$
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-1}{2*-1}=\frac{-10}{-2}
=+5
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+1}{2*-1}=\frac{-8}{-2}
=+4
$