(x+10)(x+10)=20

Solution for (x+10)(x+10)=20 equation:

(x+10)(x+10)=20

We move all terms to the left:

(x+10)(x+10)-(20)=0

We multiply parentheses ..

(+x^2+10x+10x+100)-20=0

We get rid of parentheses

x^2+10x+10x+100-20=0

We add all the numbers together, and all the variables

x^2+20x+80=0

a = 1; b = 20; c = +80;
Δ = b2-4ac
Δ = 202-4·1·80
Δ = 80
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{80}=\sqrt{16*5}=\sqrt{16}*\sqrt{5}=4\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-4\sqrt{5}}{2*1}=\frac{-20-4\sqrt{5}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+4\sqrt{5}}{2*1}=\frac{-20+4\sqrt{5}}{2}
$