20x^2-66x-9=0

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Solution for 20x^2-66x-9=0 equation:


Simplifying
20x2 + -66x + -9 = 0

Reorder the terms:
-9 + -66x + 20x2 = 0

Solving
-9 + -66x + 20x2 = 0

Solving for variable 'x'.

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

Divide each side by '20'.
-0.45 + -3.3x + x2 = 0

Move the constant term to the right:

Add '0.45' to each side of the equation.
-0.45 + -3.3x + 0.45 + x2 = 0 + 0.45

Reorder the terms:
-0.45 + 0.45 + -3.3x + x2 = 0 + 0.45

Combine like terms: -0.45 + 0.45 = 0.00
0.00 + -3.3x + x2 = 0 + 0.45
-3.3x + x2 = 0 + 0.45

Combine like terms: 0 + 0.45 = 0.45
-3.3x + x2 = 0.45

The x term is -3.3x.  Take half its coefficient (-1.65).
Square it (2.7225) and add it to both sides.

Add '2.7225' to each side of the equation.
-3.3x + 2.7225 + x2 = 0.45 + 2.7225

Reorder the terms:
2.7225 + -3.3x + x2 = 0.45 + 2.7225

Combine like terms: 0.45 + 2.7225 = 3.1725
2.7225 + -3.3x + x2 = 3.1725

Factor a perfect square on the left side:
(x + -1.65)(x + -1.65) = 3.1725

Calculate the square root of the right side: 1.781151313

Break this problem into two subproblems by setting 
(x + -1.65) equal to 1.781151313 and -1.781151313.

Subproblem 1

x + -1.65 = 1.781151313 Simplifying x + -1.65 = 1.781151313 Reorder the terms: -1.65 + x = 1.781151313 Solving -1.65 + x = 1.781151313 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.65' to each side of the equation. -1.65 + 1.65 + x = 1.781151313 + 1.65 Combine like terms: -1.65 + 1.65 = 0.00 0.00 + x = 1.781151313 + 1.65 x = 1.781151313 + 1.65 Combine like terms: 1.781151313 + 1.65 = 3.431151313 x = 3.431151313 Simplifying x = 3.431151313

Subproblem 2

x + -1.65 = -1.781151313 Simplifying x + -1.65 = -1.781151313 Reorder the terms: -1.65 + x = -1.781151313 Solving -1.65 + x = -1.781151313 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.65' to each side of the equation. -1.65 + 1.65 + x = -1.781151313 + 1.65 Combine like terms: -1.65 + 1.65 = 0.00 0.00 + x = -1.781151313 + 1.65 x = -1.781151313 + 1.65 Combine like terms: -1.781151313 + 1.65 = -0.131151313 x = -0.131151313 Simplifying x = -0.131151313

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.431151313, -0.131151313}

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