7x(3+x)=136

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Solution for 7x(3+x)=136 equation:


Simplifying
7x(3 + x) = 136
(3 * 7x + x * 7x) = 136
(21x + 7x2) = 136

Solving
21x + 7x2 = 136

Solving for variable 'x'.

Reorder the terms:
-136 + 21x + 7x2 = 136 + -136

Combine like terms: 136 + -136 = 0
-136 + 21x + 7x2 = 0

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

Divide each side by '7'.
-19.42857143 + 3x + x2 = 0

Move the constant term to the right:

Add '19.42857143' to each side of the equation.
-19.42857143 + 3x + 19.42857143 + x2 = 0 + 19.42857143

Reorder the terms:
-19.42857143 + 19.42857143 + 3x + x2 = 0 + 19.42857143

Combine like terms: -19.42857143 + 19.42857143 = 0.00000000
0.00000000 + 3x + x2 = 0 + 19.42857143
3x + x2 = 0 + 19.42857143

Combine like terms: 0 + 19.42857143 = 19.42857143
3x + x2 = 19.42857143

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 = 19.42857143 + 2.25

Reorder the terms:
2.25 + 3x + x2 = 19.42857143 + 2.25

Combine like terms: 19.42857143 + 2.25 = 21.67857143
2.25 + 3x + x2 = 21.67857143

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 21.67857143

Calculate the square root of the right side: 4.656025282

Break this problem into two subproblems by setting 
(x + 1.5) equal to 4.656025282 and -4.656025282.

Subproblem 1

x + 1.5 = 4.656025282 Simplifying x + 1.5 = 4.656025282 Reorder the terms: 1.5 + x = 4.656025282 Solving 1.5 + x = 4.656025282 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 = 4.656025282 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 4.656025282 + -1.5 x = 4.656025282 + -1.5 Combine like terms: 4.656025282 + -1.5 = 3.156025282 x = 3.156025282 Simplifying x = 3.156025282

Subproblem 2

x + 1.5 = -4.656025282 Simplifying x + 1.5 = -4.656025282 Reorder the terms: 1.5 + x = -4.656025282 Solving 1.5 + x = -4.656025282 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 = -4.656025282 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -4.656025282 + -1.5 x = -4.656025282 + -1.5 Combine like terms: -4.656025282 + -1.5 = -6.156025282 x = -6.156025282 Simplifying x = -6.156025282

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.156025282, -6.156025282}

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