x^2-28x-408=0

Solution for x^2-28x-408=0 equation:

x^2-28x-408=0

a = 1; b = -28; c = -408;
Δ = b2-4ac
Δ = -282-4·1·(-408)
Δ = 2416
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:

$\sqrt{\Delta}=\sqrt{2416}=\sqrt{16*151}=\sqrt{16}*\sqrt{151}=4\sqrt{151}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-4\sqrt{151}}{2*1}=\frac{28-4\sqrt{151}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+4\sqrt{151}}{2*1}=\frac{28+4\sqrt{151}}{2}
$