x2-400x-660=0

Solution for x2-400x-660=0 equation:

x2-400x-660=0

We add all the numbers together, and all the variables

x^2-400x-660=0

a = 1; b = -400; c = -660;
Δ = b2-4ac
Δ = -4002-4·1·(-660)
Δ = 162640
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:

$\sqrt{\Delta}=\sqrt{162640}=\sqrt{16*10165}=\sqrt{16}*\sqrt{10165}=4\sqrt{10165}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-400)-4\sqrt{10165}}{2*1}=\frac{400-4\sqrt{10165}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-400)+4\sqrt{10165}}{2*1}=\frac{400+4\sqrt{10165}}{2}
$