x^2-1.28x-1.28=0

Solution for x^2-1.28x-1.28=0 equation:

x^2-1.28x-1.28=0

a = 1; b = -1.28; c = -1.28;
Δ = b2-4ac
Δ = -1.282-4·1·(-1.28)
Δ = 6.7584
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{-(-1.28)-\sqrt{6.7584}}{2*1}=\frac{1.28-\sqrt{6.7584}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.28)+\sqrt{6.7584}}{2*1}=\frac{1.28+\sqrt{6.7584}}{2}
$