4x^2+18x+81=120

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Solution for 4x^2+18x+81=120 equation:


Simplifying
4x2 + 18x + 81 = 120

Reorder the terms:
81 + 18x + 4x2 = 120

Solving
81 + 18x + 4x2 = 120

Solving for variable 'x'.

Reorder the terms:
81 + -120 + 18x + 4x2 = 120 + -120

Combine like terms: 81 + -120 = -39
-39 + 18x + 4x2 = 120 + -120

Combine like terms: 120 + -120 = 0
-39 + 18x + 4x2 = 0

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

Divide each side by '4'.
-9.75 + 4.5x + x2 = 0

Move the constant term to the right:

Add '9.75' to each side of the equation.
-9.75 + 4.5x + 9.75 + x2 = 0 + 9.75

Reorder the terms:
-9.75 + 9.75 + 4.5x + x2 = 0 + 9.75

Combine like terms: -9.75 + 9.75 = 0.00
0.00 + 4.5x + x2 = 0 + 9.75
4.5x + x2 = 0 + 9.75

Combine like terms: 0 + 9.75 = 9.75
4.5x + x2 = 9.75

The x term is 4.5x.  Take half its coefficient (2.25).
Square it (5.0625) and add it to both sides.

Add '5.0625' to each side of the equation.
4.5x + 5.0625 + x2 = 9.75 + 5.0625

Reorder the terms:
5.0625 + 4.5x + x2 = 9.75 + 5.0625

Combine like terms: 9.75 + 5.0625 = 14.8125
5.0625 + 4.5x + x2 = 14.8125

Factor a perfect square on the left side:
(x + 2.25)(x + 2.25) = 14.8125

Calculate the square root of the right side: 3.84870108

Break this problem into two subproblems by setting 
(x + 2.25) equal to 3.84870108 and -3.84870108.

Subproblem 1

x + 2.25 = 3.84870108 Simplifying x + 2.25 = 3.84870108 Reorder the terms: 2.25 + x = 3.84870108 Solving 2.25 + x = 3.84870108 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.25' to each side of the equation. 2.25 + -2.25 + x = 3.84870108 + -2.25 Combine like terms: 2.25 + -2.25 = 0.00 0.00 + x = 3.84870108 + -2.25 x = 3.84870108 + -2.25 Combine like terms: 3.84870108 + -2.25 = 1.59870108 x = 1.59870108 Simplifying x = 1.59870108

Subproblem 2

x + 2.25 = -3.84870108 Simplifying x + 2.25 = -3.84870108 Reorder the terms: 2.25 + x = -3.84870108 Solving 2.25 + x = -3.84870108 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.25' to each side of the equation. 2.25 + -2.25 + x = -3.84870108 + -2.25 Combine like terms: 2.25 + -2.25 = 0.00 0.00 + x = -3.84870108 + -2.25 x = -3.84870108 + -2.25 Combine like terms: -3.84870108 + -2.25 = -6.09870108 x = -6.09870108 Simplifying x = -6.09870108

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.59870108, -6.09870108}

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