X-0.005x^2=40

Solution for X-0.005x^2=40 equation:

X-0.005X^2=40

We move all terms to the left:

X-0.005X^2-(40)=0

a = -0.005; b = 1; c = -40;
Δ = b2-4ac
Δ = 12-4·(-0.005)·(-40)
Δ = 0.2
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)-\sqrt{0.2}}{2*-0.005}=\frac{-1-\sqrt{0.2}}{-0.01}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{0.2}}{2*-0.005}=\frac{-1+\sqrt{0.2}}{-0.01}
$