(x+0.8)(x-1.3)=0.2

Solution for (x+0.8)(x-1.3)=0.2 equation:

(x+0.8)(x-1.3)=0.2

We move all terms to the left:

(x+0.8)(x-1.3)-(0.2)=0

We add all the numbers together, and all the variables

(x+0.8)(x-1.3)-0.2=0

We multiply parentheses ..

(+x^2-1.3x+0.8x-1.04)-0.2=0

We get rid of parentheses

x^2-1.3x+0.8x-1.04-0.2=0

We add all the numbers together, and all the variables

x^2-0.5x-1.24=0

a = 1; b = -0.5; c = -1.24;
Δ = b2-4ac
Δ = -0.52-4·1·(-1.24)
Δ = 5.21
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{-(-0.5)-\sqrt{5.21}}{2*1}=\frac{0.5-\sqrt{5.21}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.5)+\sqrt{5.21}}{2*1}=\frac{0.5+\sqrt{5.21}}{2}
$