0=-0.25d^2+5d+80

Solution for 0=-0.25d^2+5d+80 equation:

0=-0.25d^2+5d+80

We move all terms to the left:

0-(-0.25d^2+5d+80)=0

We add all the numbers together, and all the variables

-(-0.25d^2+5d+80)=0

We get rid of parentheses

0.25d^2-5d-80=0

a = 0.25; b = -5; c = -80;
Δ = b2-4ac
Δ = -52-4·0.25·(-80)
Δ = 105
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{-(-5)-\sqrt{105}}{2*0.25}=\frac{5-\sqrt{105}}{0.5}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+\sqrt{105}}{2*0.25}=\frac{5+\sqrt{105}}{0.5}
$