0=5x^2-400

Solution for 0=5x^2-400 equation:

0=5x^2-400

We move all terms to the left:

0-(5x^2-400)=0

We add all the numbers together, and all the variables

-(5x^2-400)=0

We get rid of parentheses

-5x^2+400=0

a = -5; b = 0; c = +400;
Δ = b2-4ac
Δ = 02-4·(-5)·400
Δ = 8000
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:

$\sqrt{\Delta}=\sqrt{8000}=\sqrt{1600*5}=\sqrt{1600}*\sqrt{5}=40\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-40\sqrt{5}}{2*-5}=\frac{0-40\sqrt{5}}{-10}
=-\frac{40\sqrt{5}}{-10}
=-\frac{4\sqrt{5}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+40\sqrt{5}}{2*-5}=\frac{0+40\sqrt{5}}{-10}
=\frac{40\sqrt{5}}{-10}
=\frac{4\sqrt{5}}{-1}
$