12x^2+84x-121=0

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Solution for 12x^2+84x-121=0 equation:


Simplifying
12x2 + 84x + -121 = 0

Reorder the terms:
-121 + 84x + 12x2 = 0

Solving
-121 + 84x + 12x2 = 0

Solving for variable 'x'.

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

Divide each side by '12'.
-10.08333333 + 7x + x2 = 0

Move the constant term to the right:

Add '10.08333333' to each side of the equation.
-10.08333333 + 7x + 10.08333333 + x2 = 0 + 10.08333333

Reorder the terms:
-10.08333333 + 10.08333333 + 7x + x2 = 0 + 10.08333333

Combine like terms: -10.08333333 + 10.08333333 = 0.00000000
0.00000000 + 7x + x2 = 0 + 10.08333333
7x + x2 = 0 + 10.08333333

Combine like terms: 0 + 10.08333333 = 10.08333333
7x + x2 = 10.08333333

The x term is 7x.  Take half its coefficient (3.5).
Square it (12.25) and add it to both sides.

Add '12.25' to each side of the equation.
7x + 12.25 + x2 = 10.08333333 + 12.25

Reorder the terms:
12.25 + 7x + x2 = 10.08333333 + 12.25

Combine like terms: 10.08333333 + 12.25 = 22.33333333
12.25 + 7x + x2 = 22.33333333

Factor a perfect square on the left side:
(x + 3.5)(x + 3.5) = 22.33333333

Calculate the square root of the right side: 4.725815626

Break this problem into two subproblems by setting 
(x + 3.5) equal to 4.725815626 and -4.725815626.

Subproblem 1

x + 3.5 = 4.725815626 Simplifying x + 3.5 = 4.725815626 Reorder the terms: 3.5 + x = 4.725815626 Solving 3.5 + x = 4.725815626 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.5' to each side of the equation. 3.5 + -3.5 + x = 4.725815626 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + x = 4.725815626 + -3.5 x = 4.725815626 + -3.5 Combine like terms: 4.725815626 + -3.5 = 1.225815626 x = 1.225815626 Simplifying x = 1.225815626

Subproblem 2

x + 3.5 = -4.725815626 Simplifying x + 3.5 = -4.725815626 Reorder the terms: 3.5 + x = -4.725815626 Solving 3.5 + x = -4.725815626 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.5' to each side of the equation. 3.5 + -3.5 + x = -4.725815626 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + x = -4.725815626 + -3.5 x = -4.725815626 + -3.5 Combine like terms: -4.725815626 + -3.5 = -8.225815626 x = -8.225815626 Simplifying x = -8.225815626

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.225815626, -8.225815626}

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