3x^2-18x-39=5

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Solution for 3x^2-18x-39=5 equation:


Simplifying
3x2 + -18x + -39 = 5

Reorder the terms:
-39 + -18x + 3x2 = 5

Solving
-39 + -18x + 3x2 = 5

Solving for variable 'x'.

Reorder the terms:
-39 + -5 + -18x + 3x2 = 5 + -5

Combine like terms: -39 + -5 = -44
-44 + -18x + 3x2 = 5 + -5

Combine like terms: 5 + -5 = 0
-44 + -18x + 3x2 = 0

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

Divide each side by '3'.
-14.66666667 + -6x + x2 = 0

Move the constant term to the right:

Add '14.66666667' to each side of the equation.
-14.66666667 + -6x + 14.66666667 + x2 = 0 + 14.66666667

Reorder the terms:
-14.66666667 + 14.66666667 + -6x + x2 = 0 + 14.66666667

Combine like terms: -14.66666667 + 14.66666667 = 0.00000000
0.00000000 + -6x + x2 = 0 + 14.66666667
-6x + x2 = 0 + 14.66666667

Combine like terms: 0 + 14.66666667 = 14.66666667
-6x + x2 = 14.66666667

The x term is -6x.  Take half its coefficient (-3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
-6x + 9 + x2 = 14.66666667 + 9

Reorder the terms:
9 + -6x + x2 = 14.66666667 + 9

Combine like terms: 14.66666667 + 9 = 23.66666667
9 + -6x + x2 = 23.66666667

Factor a perfect square on the left side:
(x + -3)(x + -3) = 23.66666667

Calculate the square root of the right side: 4.86483984

Break this problem into two subproblems by setting 
(x + -3) equal to 4.86483984 and -4.86483984.

Subproblem 1

x + -3 = 4.86483984 Simplifying x + -3 = 4.86483984 Reorder the terms: -3 + x = 4.86483984 Solving -3 + x = 4.86483984 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3' to each side of the equation. -3 + 3 + x = 4.86483984 + 3 Combine like terms: -3 + 3 = 0 0 + x = 4.86483984 + 3 x = 4.86483984 + 3 Combine like terms: 4.86483984 + 3 = 7.86483984 x = 7.86483984 Simplifying x = 7.86483984

Subproblem 2

x + -3 = -4.86483984 Simplifying x + -3 = -4.86483984 Reorder the terms: -3 + x = -4.86483984 Solving -3 + x = -4.86483984 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3' to each side of the equation. -3 + 3 + x = -4.86483984 + 3 Combine like terms: -3 + 3 = 0 0 + x = -4.86483984 + 3 x = -4.86483984 + 3 Combine like terms: -4.86483984 + 3 = -1.86483984 x = -1.86483984 Simplifying x = -1.86483984

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.86483984, -1.86483984}

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