4=0.4(3d-5)d

Solution for 4=0.4(3d-5)d equation:

4=0.4(3d-5)d

We move all terms to the left:

4-(0.4(3d-5)d)=0


We calculate terms in parentheses: -(0.4(3d-5)d), so:

0.4(3d-5)d

We multiply parentheses

0d^2+0d

We add all the numbers together, and all the variables

d^2+d

Back to the equation:

-(d^2+d)


We get rid of parentheses

-d^2-d+4=0

We add all the numbers together, and all the variables

-1d^2-1d+4=0

a = -1; b = -1; c = +4;
Δ = b2-4ac
Δ = -12-4·(-1)·4
Δ = 17
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{-(-1)-\sqrt{17}}{2*-1}=\frac{1-\sqrt{17}}{-2}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+\sqrt{17}}{2*-1}=\frac{1+\sqrt{17}}{-2}
$