9x^2-x-21=0

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Solution for 9x^2-x-21=0 equation:


Simplifying
9x2 + -1x + -21 = 0

Reorder the terms:
-21 + -1x + 9x2 = 0

Solving
-21 + -1x + 9x2 = 0

Solving for variable 'x'.

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

Divide each side by '9'.
-2.333333333 + -0.1111111111x + x2 = 0

Move the constant term to the right:

Add '2.333333333' to each side of the equation.
-2.333333333 + -0.1111111111x + 2.333333333 + x2 = 0 + 2.333333333

Reorder the terms:
-2.333333333 + 2.333333333 + -0.1111111111x + x2 = 0 + 2.333333333

Combine like terms: -2.333333333 + 2.333333333 = 0.000000000
0.000000000 + -0.1111111111x + x2 = 0 + 2.333333333
-0.1111111111x + x2 = 0 + 2.333333333

Combine like terms: 0 + 2.333333333 = 2.333333333
-0.1111111111x + x2 = 2.333333333

The x term is -0.1111111111x.  Take half its coefficient (-0.05555555555).
Square it (0.003086419752) and add it to both sides.

Add '0.003086419752' to each side of the equation.
-0.1111111111x + 0.003086419752 + x2 = 2.333333333 + 0.003086419752

Reorder the terms:
0.003086419752 + -0.1111111111x + x2 = 2.333333333 + 0.003086419752

Combine like terms: 2.333333333 + 0.003086419752 = 2.336419752752
0.003086419752 + -0.1111111111x + x2 = 2.336419752752

Factor a perfect square on the left side:
(x + -0.05555555555)(x + -0.05555555555) = 2.336419752752

Calculate the square root of the right side: 1.528535166

Break this problem into two subproblems by setting 
(x + -0.05555555555) equal to 1.528535166 and -1.528535166.

Subproblem 1

x + -0.05555555555 = 1.528535166 Simplifying x + -0.05555555555 = 1.528535166 Reorder the terms: -0.05555555555 + x = 1.528535166 Solving -0.05555555555 + x = 1.528535166 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.05555555555' to each side of the equation. -0.05555555555 + 0.05555555555 + x = 1.528535166 + 0.05555555555 Combine like terms: -0.05555555555 + 0.05555555555 = 0.00000000000 0.00000000000 + x = 1.528535166 + 0.05555555555 x = 1.528535166 + 0.05555555555 Combine like terms: 1.528535166 + 0.05555555555 = 1.58409072155 x = 1.58409072155 Simplifying x = 1.58409072155

Subproblem 2

x + -0.05555555555 = -1.528535166 Simplifying x + -0.05555555555 = -1.528535166 Reorder the terms: -0.05555555555 + x = -1.528535166 Solving -0.05555555555 + x = -1.528535166 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.05555555555' to each side of the equation. -0.05555555555 + 0.05555555555 + x = -1.528535166 + 0.05555555555 Combine like terms: -0.05555555555 + 0.05555555555 = 0.00000000000 0.00000000000 + x = -1.528535166 + 0.05555555555 x = -1.528535166 + 0.05555555555 Combine like terms: -1.528535166 + 0.05555555555 = -1.47297961045 x = -1.47297961045 Simplifying x = -1.47297961045

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.58409072155, -1.47297961045}

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