(8-x)(8+x)=-36

Solution for (8-x)(8+x)=-36 equation:

(8-x)(8+x)=-36

We move all terms to the left:

(8-x)(8+x)-(-36)=0

We add all the numbers together, and all the variables

(-1x+8)(x+8)-(-36)=0

We add all the numbers together, and all the variables

(-1x+8)(x+8)+36=0

We multiply parentheses ..

(-1x^2-8x+8x+64)+36=0

We get rid of parentheses

-1x^2-8x+8x+64+36=0

We add all the numbers together, and all the variables

-1x^2+100=0

a = -1; b = 0; c = +100;
Δ = b2-4ac
Δ = 02-4·(-1)·100
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-20}{2*-1}=\frac{-20}{-2}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+20}{2*-1}=\frac{20}{-2}
=-10
$