c^2=15^2+20^2

Solution for c^2=15^2+20^2 equation:

c^2=15^2+20^2

We move all terms to the left:

c^2-(15^2+20^2)=0

We add all the numbers together, and all the variables

c^2-625=0

a = 1; b = 0; c = -625;
Δ = b2-4ac
Δ = 02-4·1·(-625)
Δ = 2500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2500}=50$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-50}{2*1}=\frac{-50}{2}
=-25
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+50}{2*1}=\frac{50}{2}
=25
$