d^2+4=-4d^2+10d+0,8

Solution for d^2+4=-4d^2+10d+0,8 equation:

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

We move all terms to the left:

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

We get rid of parentheses

d^2+4d^2-10d-0.8+4=0

We add all the numbers together, and all the variables

5d^2-10d+3.2=0

a = 5; b = -10; c = +3.2;
Δ = b2-4ac
Δ = -102-4·5·3.2
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-6}{2*5}=\frac{4}{10}
=2/5
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+6}{2*5}=\frac{16}{10}
=1+3/5
$