21x^2-156x+7=0

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Solution for 21x^2-156x+7=0 equation:


Simplifying
21x2 + -156x + 7 = 0

Reorder the terms:
7 + -156x + 21x2 = 0

Solving
7 + -156x + 21x2 = 0

Solving for variable 'x'.

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

Divide each side by '21'.
0.3333333333 + -7.428571429x + x2 = 0

Move the constant term to the right:

Add '-0.3333333333' to each side of the equation.
0.3333333333 + -7.428571429x + -0.3333333333 + x2 = 0 + -0.3333333333

Reorder the terms:
0.3333333333 + -0.3333333333 + -7.428571429x + x2 = 0 + -0.3333333333

Combine like terms: 0.3333333333 + -0.3333333333 = 0.0000000000
0.0000000000 + -7.428571429x + x2 = 0 + -0.3333333333
-7.428571429x + x2 = 0 + -0.3333333333

Combine like terms: 0 + -0.3333333333 = -0.3333333333
-7.428571429x + x2 = -0.3333333333

The x term is -7.428571429x.  Take half its coefficient (-3.714285715).
Square it (13.79591837) and add it to both sides.

Add '13.79591837' to each side of the equation.
-7.428571429x + 13.79591837 + x2 = -0.3333333333 + 13.79591837

Reorder the terms:
13.79591837 + -7.428571429x + x2 = -0.3333333333 + 13.79591837

Combine like terms: -0.3333333333 + 13.79591837 = 13.4625850367
13.79591837 + -7.428571429x + x2 = 13.4625850367

Factor a perfect square on the left side:
(x + -3.714285715)(x + -3.714285715) = 13.4625850367

Calculate the square root of the right side: 3.66913955

Break this problem into two subproblems by setting 
(x + -3.714285715) equal to 3.66913955 and -3.66913955.

Subproblem 1

x + -3.714285715 = 3.66913955 Simplifying x + -3.714285715 = 3.66913955 Reorder the terms: -3.714285715 + x = 3.66913955 Solving -3.714285715 + x = 3.66913955 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.714285715' to each side of the equation. -3.714285715 + 3.714285715 + x = 3.66913955 + 3.714285715 Combine like terms: -3.714285715 + 3.714285715 = 0.000000000 0.000000000 + x = 3.66913955 + 3.714285715 x = 3.66913955 + 3.714285715 Combine like terms: 3.66913955 + 3.714285715 = 7.383425265 x = 7.383425265 Simplifying x = 7.383425265

Subproblem 2

x + -3.714285715 = -3.66913955 Simplifying x + -3.714285715 = -3.66913955 Reorder the terms: -3.714285715 + x = -3.66913955 Solving -3.714285715 + x = -3.66913955 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.714285715' to each side of the equation. -3.714285715 + 3.714285715 + x = -3.66913955 + 3.714285715 Combine like terms: -3.714285715 + 3.714285715 = 0.000000000 0.000000000 + x = -3.66913955 + 3.714285715 x = -3.66913955 + 3.714285715 Combine like terms: -3.66913955 + 3.714285715 = 0.045146165 x = 0.045146165 Simplifying x = 0.045146165

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.383425265, 0.045146165}

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