1+0.8x+0.15x^2=0

Solution for 1+0.8x+0.15x^2=0 equation:

1+0.8x+0.15x^2=0

a = 0.15; b = 0.8; c = +1;
Δ = b2-4ac
Δ = 0.82-4·0.15·1
Δ = 0.04
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{-(0.8)-\sqrt{0.04}}{2*0.15}=\frac{-0.8-\sqrt{0.04}}{0.3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.8)+\sqrt{0.04}}{2*0.15}=\frac{-0.8+\sqrt{0.04}}{0.3}
$