X^2+20x-280=0

Solution for X^2+20x-280=0 equation:

X^2+20X-280=0

a = 1; b = 20; c = -280;
Δ = b2-4ac
Δ = 202-4·1·(-280)
Δ = 1520
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:

$\sqrt{\Delta}=\sqrt{1520}=\sqrt{16*95}=\sqrt{16}*\sqrt{95}=4\sqrt{95}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-4\sqrt{95}}{2*1}=\frac{-20-4\sqrt{95}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+4\sqrt{95}}{2*1}=\frac{-20+4\sqrt{95}}{2}
$