1.2=-0.2d^2+2d

Solution for 1.2=-0.2d^2+2d equation:

1.2=-0.2d^2+2d

We move all terms to the left:

1.2-(-0.2d^2+2d)=0

We get rid of parentheses

0.2d^2-2d+1.2=0

a = 0.2; b = -2; c = +1.2;
Δ = b2-4ac
Δ = -22-4·0.2·1.2
Δ = 3.04
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{-(-2)-\sqrt{3.04}}{2*0.2}=\frac{2-\sqrt{3.04}}{0.4}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+\sqrt{3.04}}{2*0.2}=\frac{2+\sqrt{3.04}}{0.4}
$