-16d(d+1)=-20

Solution for -16d(d+1)=-20 equation:

-16d(d+1)=-20

We move all terms to the left:

-16d(d+1)-(-20)=0

We add all the numbers together, and all the variables

-16d(d+1)+20=0

We multiply parentheses

-16d^2-16d+20=0

a = -16; b = -16; c = +20;
Δ = b2-4ac
Δ = -162-4·(-16)·20
Δ = 1536
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1536}=\sqrt{256*6}=\sqrt{256}*\sqrt{6}=16\sqrt{6}$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-16\sqrt{6}}{2*-16}=\frac{16-16\sqrt{6}}{-32}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+16\sqrt{6}}{2*-16}=\frac{16+16\sqrt{6}}{-32}
$