-2a^2-16a=20

Solution for -2a^2-16a=20 equation:

-2a^2-16a=20

We move all terms to the left:

-2a^2-16a-(20)=0

a = -2; b = -16; c = -20;
Δ = b2-4ac
Δ = -162-4·(-2)·(-20)
Δ = 96
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{96}=\sqrt{16*6}=\sqrt{16}*\sqrt{6}=4\sqrt{6}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-4\sqrt{6}}{2*-2}=\frac{16-4\sqrt{6}}{-4}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+4\sqrt{6}}{2*-2}=\frac{16+4\sqrt{6}}{-4}
$