-2x(x+10)=16

Solution for -2x(x+10)=16 equation:

-2x(x+10)=16

We move all terms to the left:

-2x(x+10)-(16)=0

We multiply parentheses

-2x^2-20x-16=0

a = -2; b = -20; c = -16;
Δ = b2-4ac
Δ = -202-4·(-2)·(-16)
Δ = 272
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:

$\sqrt{\Delta}=\sqrt{272}=\sqrt{16*17}=\sqrt{16}*\sqrt{17}=4\sqrt{17}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-4\sqrt{17}}{2*-2}=\frac{20-4\sqrt{17}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+4\sqrt{17}}{2*-2}=\frac{20+4\sqrt{17}}{-4}
$