-28=-7(3x+4)21x

Solution for -28=-7(3x+4)21x equation:

Simplifying
-28 = -7(3x + 4) * 21x

Reorder the terms:
-28 = -7(4 + 3x) * 21x

Reorder the terms for easier multiplication:
-28 = -7 * 21x(4 + 3x)

Multiply -7 * 21
-28 = -147x(4 + 3x)
-28 = (4 * -147x + 3x * -147x)
-28 = (-588x + -441x2)

Solving
-28 = -588x + -441x2

Solving for variable 'x'.

Reorder the terms:
-28 + 588x + 441x2 = -588x + 588x + -441x2 + 441x2

Combine like terms: -588x + 588x = 0
-28 + 588x + 441x2 = 0 + -441x2 + 441x2
-28 + 588x + 441x2 = -441x2 + 441x2

Combine like terms: -441x2 + 441x2 = 0
-28 + 588x + 441x2 = 0

Factor out the Greatest Common Factor (GCF), '7'.
7(-4 + 84x + 63x2) = 0

Ignore the factor 7.
Subproblem 1
Set the factor '(-4 + 84x + 63x2)' equal to zero and attempt to solve:

Simplifying
-4 + 84x + 63x2 = 0

Solving
-4 + 84x + 63x2 = 0

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

Divide each side by '63'.
-0.06349206349 + 1.333333333x + x2 = 0

Move the constant term to the right:

Add '0.06349206349' to each side of the equation.
-0.06349206349 + 1.333333333x + 0.06349206349 + x2 = 0 + 0.06349206349

Reorder the terms:
-0.06349206349 + 0.06349206349 + 1.333333333x + x2 = 0 + 0.06349206349

Combine like terms: -0.06349206349 + 0.06349206349 = 0.00000000000
0.00000000000 + 1.333333333x + x2 = 0 + 0.06349206349
1.333333333x + x2 = 0 + 0.06349206349

Combine like terms: 0 + 0.06349206349 = 0.06349206349
1.333333333x + x2 = 0.06349206349

The x term is 1.333333333x.  Take half its coefficient (0.6666666665).
Square it (0.4444444442) and add it to both sides.

Add '0.4444444442' to each side of the equation.
1.333333333x + 0.4444444442 + x2 = 0.06349206349 + 0.4444444442

Reorder the terms:
0.4444444442 + 1.333333333x + x2 = 0.06349206349 + 0.4444444442

Combine like terms: 0.06349206349 + 0.4444444442 = 0.50793650769
0.4444444442 + 1.333333333x + x2 = 0.50793650769

Factor a perfect square on the left side:
(x + 0.6666666665)(x + 0.6666666665) = 0.50793650769

Calculate the square root of the right side: 0.712696645

Break this problem into two subproblems by setting 
(x + 0.6666666665) equal to 0.712696645 and -0.712696645.

Subproblem 1
x + 0.6666666665 = 0.712696645

Simplifying
x + 0.6666666665 = 0.712696645

Reorder the terms:
0.6666666665 + x = 0.712696645

Solving
0.6666666665 + x = 0.712696645

Solving for variable 'x'.

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

Add '-0.6666666665' to each side of the equation.
0.6666666665 + -0.6666666665 + x = 0.712696645 + -0.6666666665

Combine like terms: 0.6666666665 + -0.6666666665 = 0.0000000000
0.0000000000 + x = 0.712696645 + -0.6666666665
x = 0.712696645 + -0.6666666665

Combine like terms: 0.712696645 + -0.6666666665 = 0.0460299785
x = 0.0460299785

Simplifying
x = 0.0460299785

Subproblem 2
x + 0.6666666665 = -0.712696645

Simplifying
x + 0.6666666665 = -0.712696645

Reorder the terms:
0.6666666665 + x = -0.712696645

Solving
0.6666666665 + x = -0.712696645

Solving for variable 'x'.

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

Add '-0.6666666665' to each side of the equation.
0.6666666665 + -0.6666666665 + x = -0.712696645 + -0.6666666665

Combine like terms: 0.6666666665 + -0.6666666665 = 0.0000000000
0.0000000000 + x = -0.712696645 + -0.6666666665
x = -0.712696645 + -0.6666666665

Combine like terms: -0.712696645 + -0.6666666665 = -1.3793633115
x = -1.3793633115

Simplifying
x = -1.3793633115

Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {0.0460299785, -1.3793633115}
Solution
x = {0.0460299785, -1.3793633115}