X^2+20x-16=-1

Solution for X^2+20x-16=-1 equation:

X^2+20X-16=-1

We move all terms to the left:

X^2+20X-16-(-1)=0

We add all the numbers together, and all the variables

X^2+20X-15=0

a = 1; b = 20; c = -15;
Δ = b2-4ac
Δ = 202-4·1·(-15)
Δ = 460
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:

$\sqrt{\Delta}=\sqrt{460}=\sqrt{4*115}=\sqrt{4}*\sqrt{115}=2\sqrt{115}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-2\sqrt{115}}{2*1}=\frac{-20-2\sqrt{115}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+2\sqrt{115}}{2*1}=\frac{-20+2\sqrt{115}}{2}
$