0.4x^2+2x+8.1=90000

Solution for 0.4x^2+2x+8.1=90000 equation:

0.4x^2+2x+8.1=90000

We move all terms to the left:

0.4x^2+2x+8.1-(90000)=0

We add all the numbers together, and all the variables

0.4x^2+2x-89991.9=0

a = 0.4; b = 2; c = -89991.9;
Δ = b2-4ac
Δ = 22-4·0.4·(-89991.9)
Δ = 143991.04
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{-(2)-\sqrt{143991.04}}{2*0.4}=\frac{-2-\sqrt{143991.04}}{0.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+\sqrt{143991.04}}{2*0.4}=\frac{-2+\sqrt{143991.04}}{0.8}
$