X2+20x=-84

Solution for X2+20x=-84 equation:

X2+20X=-84

We move all terms to the left:

X2+20X-(-84)=0

We add all the numbers together, and all the variables

X^2+20X+84=0

a = 1; b = 20; c = +84;
Δ = b2-4ac
Δ = 202-4·1·84
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-8}{2*1}=\frac{-28}{2}
=-14
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+8}{2*1}=\frac{-12}{2}
=-6
$