0=0.004x^2+0.02x-9

Solution for 0=0.004x^2+0.02x-9 equation:

0=0.004x^2+0.02x-9

We move all terms to the left:

0-(0.004x^2+0.02x-9)=0

We add all the numbers together, and all the variables

-(0.004x^2+0.02x-9)=0

We get rid of parentheses

-0.004x^2-0.02x+9=0

a = -0.004; b = -0.02; c = +9;
Δ = b2-4ac
Δ = -0.022-4·(-0.004)·9
Δ = 0.1444
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-0.02)-\sqrt{0.1444}}{2*-0.004}=\frac{0.02-\sqrt{0.1444}}{-0.008}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.02)+\sqrt{0.1444}}{2*-0.004}=\frac{0.02+\sqrt{0.1444}}{-0.008}
$