X^2+y^2=30^2

Solution for X^2+y^2=30^2 equation:

X^2+X^2=30^2

We move all terms to the left:

X^2+X^2-(30^2)=0

We add all the numbers together, and all the variables

2X^2-900=0

a = 2; b = 0; c = -900;
Δ = b2-4ac
Δ = 02-4·2·(-900)
Δ = 7200
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:

$\sqrt{\Delta}=\sqrt{7200}=\sqrt{3600*2}=\sqrt{3600}*\sqrt{2}=60\sqrt{2}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-60\sqrt{2}}{2*2}=\frac{0-60\sqrt{2}}{4}
=-\frac{60\sqrt{2}}{4}
=-15\sqrt{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+60\sqrt{2}}{2*2}=\frac{0+60\sqrt{2}}{4}
=\frac{60\sqrt{2}}{4}
=15\sqrt{2}
$