(x-0.5)(x+0.8)=0

Solution for (x-0.5)(x+0.8)=0 equation:

(x-0.5)(x+0.8)=0

We multiply parentheses ..

(+x^2+0.8x-0.5x-0.4)=0

We get rid of parentheses

x^2+0.8x-0.5x-0.4=0

We add all the numbers together, and all the variables

x^2+0.3x-0.4=0

a = 1; b = 0.3; c = -0.4;
Δ = b2-4ac
Δ = 0.32-4·1·(-0.4)
Δ = 1.69
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{-(0.3)-\sqrt{1.69}}{2*1}=\frac{-0.3-\sqrt{1.69}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.3)+\sqrt{1.69}}{2*1}=\frac{-0.3+\sqrt{1.69}}{2}
$