4(5-x)2.1(6x)=-4.9

Solution for 4(5-x)2.1(6x)=-4.9 equation:

Simplifying
4(5 + -1x) * 2.1(6x) = -4.9

Remove parenthesis around (6x)
4(5 + -1x) * 2.1 * 6x = -4.9

Reorder the terms for easier multiplication:
4 * 2.1 * 6x(5 + -1x) = -4.9

Multiply 4 * 2.1
8.4 * 6x(5 + -1x) = -4.9

Multiply 8.4 * 6
50.4x(5 + -1x) = -4.9
(5 * 50.4x + -1x * 50.4x) = -4.9
(252x + -50.4x2) = -4.9

Solving
252x + -50.4x2 = -4.9

Solving for variable 'x'.

Reorder the terms:
4.9 + 252x + -50.4x2 = -4.9 + 4.9

Combine like terms: -4.9 + 4.9 = 0.0
4.9 + 252x + -50.4x2 = 0.0

Begin completing the square.  Divide all terms by
-50.4 the coefficient of the squared term: 

Divide each side by '-50.4'.
-0.09722222222 + -5x + x2 = 0

Move the constant term to the right:

Add '0.09722222222' to each side of the equation.
-0.09722222222 + -5x + 0.09722222222 + x2 = 0 + 0.09722222222

Reorder the terms:
-0.09722222222 + 0.09722222222 + -5x + x2 = 0 + 0.09722222222

Combine like terms: -0.09722222222 + 0.09722222222 = 0.00000000000
0.00000000000 + -5x + x2 = 0 + 0.09722222222
-5x + x2 = 0 + 0.09722222222

Combine like terms: 0 + 0.09722222222 = 0.09722222222
-5x + x2 = 0.09722222222

The x term is -5x.  Take half its coefficient (-2.5).
Square it (6.25) and add it to both sides.

Add '6.25' to each side of the equation.
-5x + 6.25 + x2 = 0.09722222222 + 6.25

Reorder the terms:
6.25 + -5x + x2 = 0.09722222222 + 6.25

Combine like terms: 0.09722222222 + 6.25 = 6.34722222222
6.25 + -5x + x2 = 6.34722222222

Factor a perfect square on the left side:
(x + -2.5)(x + -2.5) = 6.34722222222

Calculate the square root of the right side: 2.51936941

Break this problem into two subproblems by setting 
(x + -2.5) equal to 2.51936941 and -2.51936941.

Subproblem 1
x + -2.5 = 2.51936941

Simplifying
x + -2.5 = 2.51936941

Reorder the terms:
-2.5 + x = 2.51936941

Solving
-2.5 + x = 2.51936941

Solving for variable 'x'.

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

Add '2.5' to each side of the equation.
-2.5 + 2.5 + x = 2.51936941 + 2.5

Combine like terms: -2.5 + 2.5 = 0.0
0.0 + x = 2.51936941 + 2.5
x = 2.51936941 + 2.5

Combine like terms: 2.51936941 + 2.5 = 5.01936941
x = 5.01936941

Simplifying
x = 5.01936941

Subproblem 2
x + -2.5 = -2.51936941

Simplifying
x + -2.5 = -2.51936941

Reorder the terms:
-2.5 + x = -2.51936941

Solving
-2.5 + x = -2.51936941

Solving for variable 'x'.

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

Add '2.5' to each side of the equation.
-2.5 + 2.5 + x = -2.51936941 + 2.5

Combine like terms: -2.5 + 2.5 = 0.0
0.0 + x = -2.51936941 + 2.5
x = -2.51936941 + 2.5

Combine like terms: -2.51936941 + 2.5 = -0.01936941
x = -0.01936941

Simplifying
x = -0.01936941

Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {5.01936941, -0.01936941}