x^2-4x-392=0

Solution for x^2-4x-392=0 equation:

x^2-4x-392=0

a = 1; b = -4; c = -392;
Δ = b2-4ac
Δ = -42-4·1·(-392)
Δ = 1584
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:

$\sqrt{\Delta}=\sqrt{1584}=\sqrt{144*11}=\sqrt{144}*\sqrt{11}=12\sqrt{11}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-12\sqrt{11}}{2*1}=\frac{4-12\sqrt{11}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+12\sqrt{11}}{2*1}=\frac{4+12\sqrt{11}}{2}
$