3x(x+3)=8

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Solution for 3x(x+3)=8 equation: 


Simplifying
3x(x + 3) = 8

Reorder the terms:
3x(3 + x) = 8
(3 * 3x + x * 3x) = 8
(9x + 3x2) = 8

Solving
9x + 3x2 = 8

Solving for variable 'x'.

Reorder the terms:
-8 + 9x + 3x2 = 8 + -8

Combine like terms: 8 + -8 = 0
-8 + 9x + 3x2 = 0

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

Divide each side by '3'.
-2.666666667 + 3x + x2 = 0

Move the constant term to the right:

Add '2.666666667' to each side of the equation.
-2.666666667 + 3x + 2.666666667 + x2 = 0 + 2.666666667

Reorder the terms:
-2.666666667 + 2.666666667 + 3x + x2 = 0 + 2.666666667

Combine like terms: -2.666666667 + 2.666666667 = 0.000000000
0.000000000 + 3x + x2 = 0 + 2.666666667
3x + x2 = 0 + 2.666666667

Combine like terms: 0 + 2.666666667 = 2.666666667
3x + x2 = 2.666666667

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 = 2.666666667 + 2.25

Reorder the terms:
2.25 + 3x + x2 = 2.666666667 + 2.25

Combine like terms: 2.666666667 + 2.25 = 4.916666667
2.25 + 3x + x2 = 4.916666667

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 4.916666667

Calculate the square root of the right side: 2.217355783

Break this problem into two subproblems by setting 
(x + 1.5) equal to 2.217355783 and -2.217355783.


Subproblem 1
x + 1.5 = 2.217355783

Simplifying
x + 1.5 = 2.217355783

Reorder the terms:
1.5 + x = 2.217355783

Solving
1.5 + x = 2.217355783

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 = 2.217355783 + -1.5

Combine like terms: 1.5 + -1.5 = 0.0
0.0 + x = 2.217355783 + -1.5
x = 2.217355783 + -1.5

Combine like terms: 2.217355783 + -1.5 = 0.717355783
x = 0.717355783

Simplifying
x = 0.717355783


Subproblem 2
x + 1.5 = -2.217355783

Simplifying
x + 1.5 = -2.217355783

Reorder the terms:
1.5 + x = -2.217355783

Solving
1.5 + x = -2.217355783

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 = -2.217355783 + -1.5

Combine like terms: 1.5 + -1.5 = 0.0
0.0 + x = -2.217355783 + -1.5
x = -2.217355783 + -1.5

Combine like terms: -2.217355783 + -1.5 = -3.717355783
x = -3.717355783

Simplifying
x = -3.717355783


Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {0.717355783, -3.717355783}

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