900=b^2

Solution for 900=b^2 equation:

900=b^2

We move all terms to the left:

900-(b^2)=0

We add all the numbers together, and all the variables

-1b^2+900=0

a = -1; b = 0; c = +900;
Δ = b2-4ac
Δ = 02-4·(-1)·900
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-60}{2*-1}=\frac{-60}{-2}
=+30
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+60}{2*-1}=\frac{60}{-2}
=-30
$