D2+4=-4d2+10d+0,8

Solution for D2+4=-4d2+10d+0,8 equation:

2+4=-4D^2+10D+0.8

We move all terms to the left:

2+4-(-4D^2+10D+0.8)=0

We add all the numbers together, and all the variables

-(-4D^2+10D+0.8)+6=0

We get rid of parentheses

4D^2-10D-0.8+6=0

We add all the numbers together, and all the variables

4D^2-10D+5.2=0

a = 4; b = -10; c = +5.2;
Δ = b2-4ac
Δ = -102-4·4·5.2
Δ = 16.8
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{-(-10)-\sqrt{16.8}}{2*4}=\frac{10-\sqrt{16.8}}{8}
$
$D_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+\sqrt{16.8}}{2*4}=\frac{10+\sqrt{16.8}}{8}
$