(-0.4x^2)-x+50=0

Solution for (-0.4x^2)-x+50=0 equation:

(-0.4x^2)-x+50=0

We add all the numbers together, and all the variables

(-0.4x^2)-1x+50=0

We get rid of parentheses

-0.4x^2-1x+50=0

a = -0.4; b = -1; c = +50;
Δ = b2-4ac
Δ = -12-4·(-0.4)·50
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1)-9}{2*-0.4}=\frac{-8}{-0.8}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+9}{2*-0.4}=\frac{10}{-0.8}
=-12+0.4/0.8
$