-20=-180+2x^2

Solution for -20=-180+2x^2 equation:

-20=-180+2x^2

We move all terms to the left:

-20-(-180+2x^2)=0

We get rid of parentheses

-2x^2+180-20=0

We add all the numbers together, and all the variables

-2x^2+160=0

a = -2; b = 0; c = +160;
Δ = b2-4ac
Δ = 02-4·(-2)·160
Δ = 1280
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:

$\sqrt{\Delta}=\sqrt{1280}=\sqrt{256*5}=\sqrt{256}*\sqrt{5}=16\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-16\sqrt{5}}{2*-2}=\frac{0-16\sqrt{5}}{-4}
=-\frac{16\sqrt{5}}{-4}
=-\frac{4\sqrt{5}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+16\sqrt{5}}{2*-2}=\frac{0+16\sqrt{5}}{-4}
=\frac{16\sqrt{5}}{-4}
=\frac{4\sqrt{5}}{-1}
$