3600-400-b^2=b^2

Solution for 3600-400-b^2=b^2 equation:

3600-400-b^2=b^2

We move all terms to the left:

3600-400-b^2-(b^2)=0

We add all the numbers together, and all the variables

-2b^2+3200=0

a = -2; b = 0; c = +3200;
Δ = b2-4ac
Δ = 02-4·(-2)·3200
Δ = 25600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25600}=160$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-160}{2*-2}=\frac{-160}{-4}
=+40
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+160}{2*-2}=\frac{160}{-4}
=-40
$