-0.4x^2-5x+50=40

Solution for -0.4x^2-5x+50=40 equation:

-0.4x^2-5x+50=40

We move all terms to the left:

-0.4x^2-5x+50-(40)=0

We add all the numbers together, and all the variables

-0.4x^2-5x+10=0

a = -0.4; b = -5; c = +10;
Δ = b2-4ac
Δ = -52-4·(-0.4)·10
Δ = 41
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{-(-5)-\sqrt{41}}{2*-0.4}=\frac{5-\sqrt{41}}{-0.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+\sqrt{41}}{2*-0.4}=\frac{5+\sqrt{41}}{-0.8}
$