5x^2-15x-18=0

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Solution for 5x^2-15x-18=0 equation:


Simplifying
5x2 + -15x + -18 = 0

Reorder the terms:
-18 + -15x + 5x2 = 0

Solving
-18 + -15x + 5x2 = 0

Solving for variable 'x'.

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

Divide each side by '5'.
-3.6 + -3x + x2 = 0

Move the constant term to the right:

Add '3.6' to each side of the equation.
-3.6 + -3x + 3.6 + x2 = 0 + 3.6

Reorder the terms:
-3.6 + 3.6 + -3x + x2 = 0 + 3.6

Combine like terms: -3.6 + 3.6 = 0.0
0.0 + -3x + x2 = 0 + 3.6
-3x + x2 = 0 + 3.6

Combine like terms: 0 + 3.6 = 3.6
-3x + x2 = 3.6

The x term is -3x.  Take half its coefficient (-1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
-3x + 2.25 + x2 = 3.6 + 2.25

Reorder the terms:
2.25 + -3x + x2 = 3.6 + 2.25

Combine like terms: 3.6 + 2.25 = 5.85
2.25 + -3x + x2 = 5.85

Factor a perfect square on the left side:
(x + -1.5)(x + -1.5) = 5.85

Calculate the square root of the right side: 2.418677324

Break this problem into two subproblems by setting 
(x + -1.5) equal to 2.418677324 and -2.418677324.

Subproblem 1

x + -1.5 = 2.418677324 Simplifying x + -1.5 = 2.418677324 Reorder the terms: -1.5 + x = 2.418677324 Solving -1.5 + x = 2.418677324 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + x = 2.418677324 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x = 2.418677324 + 1.5 x = 2.418677324 + 1.5 Combine like terms: 2.418677324 + 1.5 = 3.918677324 x = 3.918677324 Simplifying x = 3.918677324

Subproblem 2

x + -1.5 = -2.418677324 Simplifying x + -1.5 = -2.418677324 Reorder the terms: -1.5 + x = -2.418677324 Solving -1.5 + x = -2.418677324 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + x = -2.418677324 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x = -2.418677324 + 1.5 x = -2.418677324 + 1.5 Combine like terms: -2.418677324 + 1.5 = -0.918677324 x = -0.918677324 Simplifying x = -0.918677324

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.918677324, -0.918677324}

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