(x^2)-28x-4=0

Solution for (x^2)-28x-4=0 equation:

(x^2)-28x-4=0

a = 1; b = -28; c = -4;
Δ = b2-4ac
Δ = -282-4·1·(-4)
Δ = 800
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:

$\sqrt{\Delta}=\sqrt{800}=\sqrt{400*2}=\sqrt{400}*\sqrt{2}=20\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-20\sqrt{2}}{2*1}=\frac{28-20\sqrt{2}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+20\sqrt{2}}{2*1}=\frac{28+20\sqrt{2}}{2}
$