8000=-5d^2+450d-1000

Solution for 8000=-5d^2+450d-1000 equation:

8000=-5d^2+450d-1000

We move all terms to the left:

8000-(-5d^2+450d-1000)=0

We get rid of parentheses

5d^2-450d+1000+8000=0

We add all the numbers together, and all the variables

5d^2-450d+9000=0

a = 5; b = -450; c = +9000;
Δ = b2-4ac
Δ = -4502-4·5·9000
Δ = 22500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{22500}=150$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-450)-150}{2*5}=\frac{300}{10}
=30
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-450)+150}{2*5}=\frac{600}{10}
=60
$