7x^2-27x-18=0

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Solution for 7x^2-27x-18=0 equation:


Simplifying
7x2 + -27x + -18 = 0

Reorder the terms:
-18 + -27x + 7x2 = 0

Solving
-18 + -27x + 7x2 = 0

Solving for variable 'x'.

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

Divide each side by '7'.
-2.571428571 + -3.857142857x + x2 = 0

Move the constant term to the right:

Add '2.571428571' to each side of the equation.
-2.571428571 + -3.857142857x + 2.571428571 + x2 = 0 + 2.571428571

Reorder the terms:
-2.571428571 + 2.571428571 + -3.857142857x + x2 = 0 + 2.571428571

Combine like terms: -2.571428571 + 2.571428571 = 0.000000000
0.000000000 + -3.857142857x + x2 = 0 + 2.571428571
-3.857142857x + x2 = 0 + 2.571428571

Combine like terms: 0 + 2.571428571 = 2.571428571
-3.857142857x + x2 = 2.571428571

The x term is -3.857142857x.  Take half its coefficient (-1.928571429).
Square it (3.719387757) and add it to both sides.

Add '3.719387757' to each side of the equation.
-3.857142857x + 3.719387757 + x2 = 2.571428571 + 3.719387757

Reorder the terms:
3.719387757 + -3.857142857x + x2 = 2.571428571 + 3.719387757

Combine like terms: 2.571428571 + 3.719387757 = 6.290816328
3.719387757 + -3.857142857x + x2 = 6.290816328

Factor a perfect square on the left side:
(x + -1.928571429)(x + -1.928571429) = 6.290816328

Calculate the square root of the right side: 2.508149981

Break this problem into two subproblems by setting 
(x + -1.928571429) equal to 2.508149981 and -2.508149981.

Subproblem 1

x + -1.928571429 = 2.508149981 Simplifying x + -1.928571429 = 2.508149981 Reorder the terms: -1.928571429 + x = 2.508149981 Solving -1.928571429 + x = 2.508149981 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.928571429' to each side of the equation. -1.928571429 + 1.928571429 + x = 2.508149981 + 1.928571429 Combine like terms: -1.928571429 + 1.928571429 = 0.000000000 0.000000000 + x = 2.508149981 + 1.928571429 x = 2.508149981 + 1.928571429 Combine like terms: 2.508149981 + 1.928571429 = 4.43672141 x = 4.43672141 Simplifying x = 4.43672141

Subproblem 2

x + -1.928571429 = -2.508149981 Simplifying x + -1.928571429 = -2.508149981 Reorder the terms: -1.928571429 + x = -2.508149981 Solving -1.928571429 + x = -2.508149981 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.928571429' to each side of the equation. -1.928571429 + 1.928571429 + x = -2.508149981 + 1.928571429 Combine like terms: -1.928571429 + 1.928571429 = 0.000000000 0.000000000 + x = -2.508149981 + 1.928571429 x = -2.508149981 + 1.928571429 Combine like terms: -2.508149981 + 1.928571429 = -0.579578552 x = -0.579578552 Simplifying x = -0.579578552

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.43672141, -0.579578552}

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