0.8-0.2x^2=-1

Solution for 0.8-0.2x^2=-1 equation:

0.8-0.2x^2=-1

We move all terms to the left:

0.8-0.2x^2-(-1)=0

We add all the numbers together, and all the variables

-0.2x^2+1.8=0

a = -0.2; b = 0; c = +1.8;
Δ = b2-4ac
Δ = 02-4·(-0.2)·1.8
Δ = 1.44
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{-(0)-\sqrt{1.44}}{2*-0.2}=\frac{0-\sqrt{1.44}}{-0.4}
=-\frac{\sqrt{}}{-0.4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{1.44}}{2*-0.2}=\frac{0+\sqrt{1.44}}{-0.4}
=\frac{\sqrt{}}{-0.4}
$