x^2+9x-66=0

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


Simplifying
x2 + 9x + -66 = 0

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

Solving
-66 + 9x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '66' to each side of the equation.
-66 + 9x + 66 + x2 = 0 + 66

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

Combine like terms: -66 + 66 = 0
0 + 9x + x2 = 0 + 66
9x + x2 = 0 + 66

Combine like terms: 0 + 66 = 66
9x + x2 = 66

The x term is 9x.  Take half its coefficient (4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
9x + 20.25 + x2 = 66 + 20.25

Reorder the terms:
20.25 + 9x + x2 = 66 + 20.25

Combine like terms: 66 + 20.25 = 86.25
20.25 + 9x + x2 = 86.25

Factor a perfect square on the left side:
(x + 4.5)(x + 4.5) = 86.25

Calculate the square root of the right side: 9.287087811

Break this problem into two subproblems by setting 
(x + 4.5) equal to 9.287087811 and -9.287087811.

Subproblem 1

x + 4.5 = 9.287087811 Simplifying x + 4.5 = 9.287087811 Reorder the terms: 4.5 + x = 9.287087811 Solving 4.5 + x = 9.287087811 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = 9.287087811 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = 9.287087811 + -4.5 x = 9.287087811 + -4.5 Combine like terms: 9.287087811 + -4.5 = 4.787087811 x = 4.787087811 Simplifying x = 4.787087811

Subproblem 2

x + 4.5 = -9.287087811 Simplifying x + 4.5 = -9.287087811 Reorder the terms: 4.5 + x = -9.287087811 Solving 4.5 + x = -9.287087811 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = -9.287087811 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = -9.287087811 + -4.5 x = -9.287087811 + -4.5 Combine like terms: -9.287087811 + -4.5 = -13.787087811 x = -13.787087811 Simplifying x = -13.787087811

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.787087811, -13.787087811}

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