Y=0.2x2-2x-4

Solution for Y=0.2x2-2x-4 equation:

=0.2Y^2-2Y-4

We move all terms to the left:

-(0.2Y^2-2Y-4)=0

We get rid of parentheses

-0.2Y^2+2Y+4=0

a = -0.2; b = 2; c = +4;
Δ = b2-4ac
Δ = 22-4·(-0.2)·4
Δ = 7.2
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-\sqrt{7.2}}{2*-0.2}=\frac{-2-\sqrt{7.2}}{-0.4}
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+\sqrt{7.2}}{2*-0.2}=\frac{-2+\sqrt{7.2}}{-0.4}
$