0=x^2+-8x-20

Solution for 0=x^2+-8x-20 equation:

0=x^2+-8x-20

We move all terms to the left:

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

We add all the numbers together, and all the variables

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

We use the square of the difference formula

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

We get rid of parentheses

-x^2+8x+20=0

We add all the numbers together, and all the variables

-1x^2+8x+20=0

a = -1; b = 8; c = +20;
Δ = b2-4ac
Δ = 82-4·(-1)·20
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-12}{2*-1}=\frac{-20}{-2}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+12}{2*-1}=\frac{4}{-2}
=-2
$