0.1x^2+0.9x^2+15X-485X+28000=0

Solution for 0.1x^2+0.9x^2+15X-485X+28000=0 equation:

0.1x^2+0.9x^2+15x-485x+28000=0

We add all the numbers together, and all the variables

x^2-470x+28000=0

a = 1; b = -470; c = +28000;
Δ = b2-4ac
Δ = -4702-4·1·28000
Δ = 108900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{108900}=330$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-470)-330}{2*1}=\frac{140}{2}
=70
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-470)+330}{2*1}=\frac{800}{2}
=400
$