x^2+20x-3900=0

Solution for x^2+20x-3900=0 equation:

x^2+20x-3900=0

a = 1; b = 20; c = -3900;
Δ = b2-4ac
Δ = 202-4·1·(-3900)
Δ = 16000
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:

$\sqrt{\Delta}=\sqrt{16000}=\sqrt{1600*10}=\sqrt{1600}*\sqrt{10}=40\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-40\sqrt{10}}{2*1}=\frac{-20-40\sqrt{10}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+40\sqrt{10}}{2*1}=\frac{-20+40\sqrt{10}}{2}
$