-4d(d+4)=0

Solution for -4d(d+4)=0 equation:

-4d(d+4)=0

We multiply parentheses

-4d^2-16d=0

a = -4; b = -16; c = 0;
Δ = b2-4ac
Δ = -162-4·(-4)·0
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-16}{2*-4}=\frac{0}{-8}
=0
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+16}{2*-4}=\frac{32}{-8}
=-4
$