0.3x^2+-0.6x=1.58

Solution for 0.3x^2+-0.6x=1.58 equation:

Simplifying
0.3x2 + -0.6x = 1.58

Reorder the terms:
-0.6x + 0.3x2 = 1.58

Solving
-0.6x + 0.3x2 = 1.58

Solving for variable 'x'.

Reorder the terms:
-1.58 + -0.6x + 0.3x2 = 1.58 + -1.58

Combine like terms: 1.58 + -1.58 = 0.00
-1.58 + -0.6x + 0.3x2 = 0.00

Begin completing the square.  Divide all terms by
0.3 the coefficient of the squared term: 

Divide each side by '0.3'.
-5.266666667 + -2x + x2 = 0.0

Move the constant term to the right:

Add '5.266666667' to each side of the equation.
-5.266666667 + -2x + 5.266666667 + x2 = 0.0 + 5.266666667

Reorder the terms:
-5.266666667 + 5.266666667 + -2x + x2 = 0.0 + 5.266666667

Combine like terms: -5.266666667 + 5.266666667 = 0.000000000
0.000000000 + -2x + x2 = 0.0 + 5.266666667
-2x + x2 = 0.0 + 5.266666667

Combine like terms: 0.0 + 5.266666667 = 5.266666667
-2x + x2 = 5.266666667

The x term is -2x.  Take half its coefficient (-1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
-2x + 1 + x2 = 5.266666667 + 1

Reorder the terms:
1 + -2x + x2 = 5.266666667 + 1

Combine like terms: 5.266666667 + 1 = 6.266666667
1 + -2x + x2 = 6.266666667

Factor a perfect square on the left side:
(x + -1)(x + -1) = 6.266666667

Calculate the square root of the right side: 2.503331114

Break this problem into two subproblems by setting 
(x + -1) equal to 2.503331114 and -2.503331114.

Subproblem 1
x + -1 = 2.503331114

Simplifying
x + -1 = 2.503331114

Reorder the terms:
-1 + x = 2.503331114

Solving
-1 + x = 2.503331114

Solving for variable 'x'.

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

Add '1' to each side of the equation.
-1 + 1 + x = 2.503331114 + 1

Combine like terms: -1 + 1 = 0
0 + x = 2.503331114 + 1
x = 2.503331114 + 1

Combine like terms: 2.503331114 + 1 = 3.503331114
x = 3.503331114

Simplifying
x = 3.503331114

Subproblem 2
x + -1 = -2.503331114

Simplifying
x + -1 = -2.503331114

Reorder the terms:
-1 + x = -2.503331114

Solving
-1 + x = -2.503331114

Solving for variable 'x'.

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

Add '1' to each side of the equation.
-1 + 1 + x = -2.503331114 + 1

Combine like terms: -1 + 1 = 0
0 + x = -2.503331114 + 1
x = -2.503331114 + 1

Combine like terms: -2.503331114 + 1 = -1.503331114
x = -1.503331114

Simplifying
x = -1.503331114

Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {3.503331114, -1.503331114}