0.2x^2-0.2-0.4=0

Solution for 0.2x^2-0.2-0.4=0 equation:

Simplifying
0.2x2 + -0.2 + -0.4 = 0

Reorder the terms:
-0.2 + -0.4 + 0.2x2 = 0

Combine like terms: -0.2 + -0.4 = -0.6
-0.6 + 0.2x2 = 0

Solving
-0.6 + 0.2x2 = 0

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '0.6' to each side of the equation.
-0.6 + 0.6 + 0.2x2 = 0 + 0.6

Combine like terms: -0.6 + 0.6 = 0.0
0.0 + 0.2x2 = 0 + 0.6
0.2x2 = 0 + 0.6

Combine like terms: 0 + 0.6 = 0.6
0.2x2 = 0.6

Divide each side by '0.2'.
x2 = 3

Simplifying
x2 = 3

Take the square root of each side:
x = {-1.732050808, 1.732050808}