u^2-20u-1600=0

Solution for u^2-20u-1600=0 equation:

u^2-20u-1600=0

a = 1; b = -20; c = -1600;
Δ = b2-4ac
Δ = -202-4·1·(-1600)
Δ = 6800
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{6800}=\sqrt{400*17}=\sqrt{400}*\sqrt{17}=20\sqrt{17}$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-20\sqrt{17}}{2*1}=\frac{20-20\sqrt{17}}{2}
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+20\sqrt{17}}{2*1}=\frac{20+20\sqrt{17}}{2}
$