-0.12*x^2-4.8*x=-200

Solution for -0.12*x^2-4.8*x=-200 equation:

-0.12x^2-4.8x=-200

We move all terms to the left:

-0.12x^2-4.8x-(-200)=0

We add all the numbers together, and all the variables

-0.12x^2-4.8x+200=0

a = -0.12; b = -4.8; c = +200;
Δ = b2-4ac
Δ = -4.82-4·(-0.12)·200
Δ = 119.04
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{-(-4.8)-\sqrt{119.04}}{2*-0.12}=\frac{4.8-\sqrt{119.04}}{-0.24}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4.8)+\sqrt{119.04}}{2*-0.12}=\frac{4.8+\sqrt{119.04}}{-0.24}
$