-0.16x^2-9.6x+256=0

Solution for -0.16x^2-9.6x+256=0 equation:

-0.16x^2-9.6x+256=0

a = -0.16; b = -9.6; c = +256;
Δ = b2-4ac
Δ = -9.62-4·(-0.16)·256
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9.6)-16}{2*-0.16}=\frac{-6.4}{-0.32}
=+20
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9.6)+16}{2*-0.16}=\frac{25.6}{-0.32}
=-80
$