x^2+400x-72000=0

Solution for x^2+400x-72000=0 equation:

x^2+400x-72000=0

a = 1; b = 400; c = -72000;
Δ = b2-4ac
Δ = 4002-4·1·(-72000)
Δ = 448000
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:

$\sqrt{\Delta}=\sqrt{448000}=\sqrt{6400*70}=\sqrt{6400}*\sqrt{70}=80\sqrt{70}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(400)-80\sqrt{70}}{2*1}=\frac{-400-80\sqrt{70}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(400)+80\sqrt{70}}{2*1}=\frac{-400+80\sqrt{70}}{2}
$