x=x2-8x-20

Solution for x=x2-8x-20 equation:

x=x2-8x-20

We move all terms to the left:

x-(x2-8x-20)=0

We add all the numbers together, and all the variables

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

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

a = -1; b = 9; c = +20;
Δ = b2-4ac
Δ = 92-4·(-1)·20
Δ = 161
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-\sqrt{161}}{2*-1}=\frac{-9-\sqrt{161}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+\sqrt{161}}{2*-1}=\frac{-9+\sqrt{161}}{-2}
$