(7x-12)(x+4)=9

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Solution for (7x-12)(x+4)=9 equation:


Simplifying
(7x + -12)(x + 4) = 9

Reorder the terms:
(-12 + 7x)(x + 4) = 9

Reorder the terms:
(-12 + 7x)(4 + x) = 9

Multiply (-12 + 7x) * (4 + x)
(-12(4 + x) + 7x * (4 + x)) = 9
((4 * -12 + x * -12) + 7x * (4 + x)) = 9
((-48 + -12x) + 7x * (4 + x)) = 9
(-48 + -12x + (4 * 7x + x * 7x)) = 9
(-48 + -12x + (28x + 7x2)) = 9

Combine like terms: -12x + 28x = 16x
(-48 + 16x + 7x2) = 9

Solving
-48 + 16x + 7x2 = 9

Solving for variable 'x'.

Reorder the terms:
-48 + -9 + 16x + 7x2 = 9 + -9

Combine like terms: -48 + -9 = -57
-57 + 16x + 7x2 = 9 + -9

Combine like terms: 9 + -9 = 0
-57 + 16x + 7x2 = 0

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

Divide each side by '7'.
-8.142857143 + 2.285714286x + x2 = 0

Move the constant term to the right:

Add '8.142857143' to each side of the equation.
-8.142857143 + 2.285714286x + 8.142857143 + x2 = 0 + 8.142857143

Reorder the terms:
-8.142857143 + 8.142857143 + 2.285714286x + x2 = 0 + 8.142857143

Combine like terms: -8.142857143 + 8.142857143 = 0.000000000
0.000000000 + 2.285714286x + x2 = 0 + 8.142857143
2.285714286x + x2 = 0 + 8.142857143

Combine like terms: 0 + 8.142857143 = 8.142857143
2.285714286x + x2 = 8.142857143

The x term is 2.285714286x.  Take half its coefficient (1.142857143).
Square it (1.306122449) and add it to both sides.

Add '1.306122449' to each side of the equation.
2.285714286x + 1.306122449 + x2 = 8.142857143 + 1.306122449

Reorder the terms:
1.306122449 + 2.285714286x + x2 = 8.142857143 + 1.306122449

Combine like terms: 8.142857143 + 1.306122449 = 9.448979592
1.306122449 + 2.285714286x + x2 = 9.448979592

Factor a perfect square on the left side:
(x + 1.142857143)(x + 1.142857143) = 9.448979592

Calculate the square root of the right side: 3.073919256

Break this problem into two subproblems by setting 
(x + 1.142857143) equal to 3.073919256 and -3.073919256.

Subproblem 1

x + 1.142857143 = 3.073919256 Simplifying x + 1.142857143 = 3.073919256 Reorder the terms: 1.142857143 + x = 3.073919256 Solving 1.142857143 + x = 3.073919256 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.142857143' to each side of the equation. 1.142857143 + -1.142857143 + x = 3.073919256 + -1.142857143 Combine like terms: 1.142857143 + -1.142857143 = 0.000000000 0.000000000 + x = 3.073919256 + -1.142857143 x = 3.073919256 + -1.142857143 Combine like terms: 3.073919256 + -1.142857143 = 1.931062113 x = 1.931062113 Simplifying x = 1.931062113

Subproblem 2

x + 1.142857143 = -3.073919256 Simplifying x + 1.142857143 = -3.073919256 Reorder the terms: 1.142857143 + x = -3.073919256 Solving 1.142857143 + x = -3.073919256 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.142857143' to each side of the equation. 1.142857143 + -1.142857143 + x = -3.073919256 + -1.142857143 Combine like terms: 1.142857143 + -1.142857143 = 0.000000000 0.000000000 + x = -3.073919256 + -1.142857143 x = -3.073919256 + -1.142857143 Combine like terms: -3.073919256 + -1.142857143 = -4.216776399 x = -4.216776399 Simplifying x = -4.216776399

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.931062113, -4.216776399}

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