x^2-0.8x+0.15=0

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

x^2-0.8x+0.15=0

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