X^2+y^2=28^2

Solution for X^2+y^2=28^2 equation:

X^2+X^2=28^2

We move all terms to the left:

X^2+X^2-(28^2)=0

We add all the numbers together, and all the variables

2X^2-784=0

a = 2; b = 0; c = -784;
Δ = b2-4ac
Δ = 02-4·2·(-784)
Δ = 6272
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:

$\sqrt{\Delta}=\sqrt{6272}=\sqrt{3136*2}=\sqrt{3136}*\sqrt{2}=56\sqrt{2}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-56\sqrt{2}}{2*2}=\frac{0-56\sqrt{2}}{4}
=-\frac{56\sqrt{2}}{4}
=-14\sqrt{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+56\sqrt{2}}{2*2}=\frac{0+56\sqrt{2}}{4}
=\frac{56\sqrt{2}}{4}
=14\sqrt{2}
$