18x^2+5x-72=0

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Solution for 18x^2+5x-72=0 equation:


Simplifying
18x2 + 5x + -72 = 0

Reorder the terms:
-72 + 5x + 18x2 = 0

Solving
-72 + 5x + 18x2 = 0

Solving for variable 'x'.

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

Divide each side by '18'.
-4 + 0.2777777778x + x2 = 0

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + 0.2777777778x + 4 + x2 = 0 + 4

Reorder the terms:
-4 + 4 + 0.2777777778x + x2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + 0.2777777778x + x2 = 0 + 4
0.2777777778x + x2 = 0 + 4

Combine like terms: 0 + 4 = 4
0.2777777778x + x2 = 4

The x term is 0.2777777778x.  Take half its coefficient (0.1388888889).
Square it (0.01929012346) and add it to both sides.

Add '0.01929012346' to each side of the equation.
0.2777777778x + 0.01929012346 + x2 = 4 + 0.01929012346

Reorder the terms:
0.01929012346 + 0.2777777778x + x2 = 4 + 0.01929012346

Combine like terms: 4 + 0.01929012346 = 4.01929012346
0.01929012346 + 0.2777777778x + x2 = 4.01929012346

Factor a perfect square on the left side:
(x + 0.1388888889)(x + 0.1388888889) = 4.01929012346

Calculate the square root of the right side: 2.004816731

Break this problem into two subproblems by setting 
(x + 0.1388888889) equal to 2.004816731 and -2.004816731.

Subproblem 1

x + 0.1388888889 = 2.004816731 Simplifying x + 0.1388888889 = 2.004816731 Reorder the terms: 0.1388888889 + x = 2.004816731 Solving 0.1388888889 + x = 2.004816731 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1388888889' to each side of the equation. 0.1388888889 + -0.1388888889 + x = 2.004816731 + -0.1388888889 Combine like terms: 0.1388888889 + -0.1388888889 = 0.0000000000 0.0000000000 + x = 2.004816731 + -0.1388888889 x = 2.004816731 + -0.1388888889 Combine like terms: 2.004816731 + -0.1388888889 = 1.8659278421 x = 1.8659278421 Simplifying x = 1.8659278421

Subproblem 2

x + 0.1388888889 = -2.004816731 Simplifying x + 0.1388888889 = -2.004816731 Reorder the terms: 0.1388888889 + x = -2.004816731 Solving 0.1388888889 + x = -2.004816731 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1388888889' to each side of the equation. 0.1388888889 + -0.1388888889 + x = -2.004816731 + -0.1388888889 Combine like terms: 0.1388888889 + -0.1388888889 = 0.0000000000 0.0000000000 + x = -2.004816731 + -0.1388888889 x = -2.004816731 + -0.1388888889 Combine like terms: -2.004816731 + -0.1388888889 = -2.1437056199 x = -2.1437056199 Simplifying x = -2.1437056199

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.8659278421, -2.1437056199}

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