-.2x^2+90x+2000=0

Solution for -.2x^2+90x+2000=0 equation:

-.2x^2+90x+2000=0

We add all the numbers together, and all the variables

-0.2x^2+90x+2000=0

a = -0.2; b = 90; c = +2000;
Δ = b2-4ac
Δ = 902-4·(-0.2)·2000
Δ = 9700
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{9700}=\sqrt{100*97}=\sqrt{100}*\sqrt{97}=10\sqrt{97}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(90)-10\sqrt{97}}{2*-0.2}=\frac{-90-10\sqrt{97}}{-0.4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(90)+10\sqrt{97}}{2*-0.2}=\frac{-90+10\sqrt{97}}{-0.4}
$