-3=0.003x^2-0.3x

Solution for -3=0.003x^2-0.3x equation:

-3=0.003x^2-0.3x

We move all terms to the left:

-3-(0.003x^2-0.3x)=0

We get rid of parentheses

-0.003x^2+0.3x-3=0

a = -0.003; b = 0.3; c = -3;
Δ = b2-4ac
Δ = 0.32-4·(-0.003)·(-3)
Δ = 0.054
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{-(0.3)-\sqrt{0.054}}{2*-0.003}=\frac{-0.3-\sqrt{0.054}}{-0.006}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.3)+\sqrt{0.054}}{2*-0.003}=\frac{-0.3+\sqrt{0.054}}{-0.006}
$