125=5x^2+20x+20

Solution for 125=5x^2+20x+20 equation:

125=5x^2+20x+20

We move all terms to the left:

125-(5x^2+20x+20)=0

We get rid of parentheses

-5x^2-20x-20+125=0

We add all the numbers together, and all the variables

-5x^2-20x+105=0

a = -5; b = -20; c = +105;
Δ = b2-4ac
Δ = -202-4·(-5)·105
Δ = 2500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2500}=50$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-50}{2*-5}=\frac{-30}{-10}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+50}{2*-5}=\frac{70}{-10}
=-7
$