18=5x^2+3x

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Solution for 18=5x^2+3x equation:


Simplifying
18 = 5x2 + 3x

Reorder the terms:
18 = 3x + 5x2

Solving
18 = 3x + 5x2

Solving for variable 'x'.

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

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

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

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

Divide each side by '-5'.
-3.6 + 0.6x + x2 = 0

Move the constant term to the right:

Add '3.6' to each side of the equation.
-3.6 + 0.6x + 3.6 + x2 = 0 + 3.6

Reorder the terms:
-3.6 + 3.6 + 0.6x + x2 = 0 + 3.6

Combine like terms: -3.6 + 3.6 = 0.0
0.0 + 0.6x + x2 = 0 + 3.6
0.6x + x2 = 0 + 3.6

Combine like terms: 0 + 3.6 = 3.6
0.6x + x2 = 3.6

The x term is 0.6x.  Take half its coefficient (0.3).
Square it (0.09) and add it to both sides.

Add '0.09' to each side of the equation.
0.6x + 0.09 + x2 = 3.6 + 0.09

Reorder the terms:
0.09 + 0.6x + x2 = 3.6 + 0.09

Combine like terms: 3.6 + 0.09 = 3.69
0.09 + 0.6x + x2 = 3.69

Factor a perfect square on the left side:
(x + 0.3)(x + 0.3) = 3.69

Calculate the square root of the right side: 1.920937271

Break this problem into two subproblems by setting 
(x + 0.3) equal to 1.920937271 and -1.920937271.

Subproblem 1

x + 0.3 = 1.920937271 Simplifying x + 0.3 = 1.920937271 Reorder the terms: 0.3 + x = 1.920937271 Solving 0.3 + x = 1.920937271 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.3' to each side of the equation. 0.3 + -0.3 + x = 1.920937271 + -0.3 Combine like terms: 0.3 + -0.3 = 0.0 0.0 + x = 1.920937271 + -0.3 x = 1.920937271 + -0.3 Combine like terms: 1.920937271 + -0.3 = 1.620937271 x = 1.620937271 Simplifying x = 1.620937271

Subproblem 2

x + 0.3 = -1.920937271 Simplifying x + 0.3 = -1.920937271 Reorder the terms: 0.3 + x = -1.920937271 Solving 0.3 + x = -1.920937271 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.3' to each side of the equation. 0.3 + -0.3 + x = -1.920937271 + -0.3 Combine like terms: 0.3 + -0.3 = 0.0 0.0 + x = -1.920937271 + -0.3 x = -1.920937271 + -0.3 Combine like terms: -1.920937271 + -0.3 = -2.220937271 x = -2.220937271 Simplifying x = -2.220937271

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.620937271, -2.220937271}

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