-x2-8x+240=0

Solution for -x2-8x+240=0 equation:

-x2-8x+240=0

We add all the numbers together, and all the variables

-1x^2-8x+240=0

a = -1; b = -8; c = +240;
Δ = b2-4ac
Δ = -82-4·(-1)·240
Δ = 1024
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1024}=32$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-32}{2*-1}=\frac{-24}{-2}
=+12
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+32}{2*-1}=\frac{40}{-2}
=-20
$