-0.2x^2=9x

Solution for -0.2x^2=9x equation:

-0.2x^2=9x

We move all terms to the left:

-0.2x^2-(9x)=0

a = -0.2; b = -9; c = 0;
Δ = b2-4ac
Δ = -92-4·(-0.2)·0
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-9}{2*-0.2}=\frac{0}{-0.4}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+9}{2*-0.2}=\frac{18}{-0.4}
=-45
$