0=-0.001d^2+0.4d-27

Solution for 0=-0.001d^2+0.4d-27 equation:

0=-0.001d^2+0.4d-27

We move all terms to the left:

0-(-0.001d^2+0.4d-27)=0

We add all the numbers together, and all the variables

-(-0.001d^2+0.4d-27)=0

We get rid of parentheses

0.001d^2-0.4d+27=0

a = 0.001; b = -0.4; c = +27;
Δ = b2-4ac
Δ = -0.42-4·0.001·27
Δ = 0.052
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-0.4)-\sqrt{0.052}}{2*0.001}=\frac{0.4-\sqrt{0.052}}{0.002}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.4)+\sqrt{0.052}}{2*0.001}=\frac{0.4+\sqrt{0.052}}{0.002}
$