-0.02x^2+0.8x+1.8=0

Solution for -0.02x^2+0.8x+1.8=0 equation:

-0.02x^2+0.8x+1.8=0

a = -0.02; b = 0.8; c = +1.8;
Δ = b2-4ac
Δ = 0.82-4·(-0.02)·1.8
Δ = 0.784
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{-(0.8)-\sqrt{0.784}}{2*-0.02}=\frac{-0.8-\sqrt{0.784}}{-0.04}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.8)+\sqrt{0.784}}{2*-0.02}=\frac{-0.8+\sqrt{0.784}}{-0.04}
$