(3x+4)(x-4)=9

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Solution for (3x+4)(x-4)=9 equation:


Simplifying
(3x + 4)(x + -4) = 9

Reorder the terms:
(4 + 3x)(x + -4) = 9

Reorder the terms:
(4 + 3x)(-4 + x) = 9

Multiply (4 + 3x) * (-4 + x)
(4(-4 + x) + 3x * (-4 + x)) = 9
((-4 * 4 + x * 4) + 3x * (-4 + x)) = 9
((-16 + 4x) + 3x * (-4 + x)) = 9
(-16 + 4x + (-4 * 3x + x * 3x)) = 9
(-16 + 4x + (-12x + 3x2)) = 9

Combine like terms: 4x + -12x = -8x
(-16 + -8x + 3x2) = 9

Solving
-16 + -8x + 3x2 = 9

Solving for variable 'x'.

Reorder the terms:
-16 + -9 + -8x + 3x2 = 9 + -9

Combine like terms: -16 + -9 = -25
-25 + -8x + 3x2 = 9 + -9

Combine like terms: 9 + -9 = 0
-25 + -8x + 3x2 = 0

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

Divide each side by '3'.
-8.333333333 + -2.666666667x + x2 = 0

Move the constant term to the right:

Add '8.333333333' to each side of the equation.
-8.333333333 + -2.666666667x + 8.333333333 + x2 = 0 + 8.333333333

Reorder the terms:
-8.333333333 + 8.333333333 + -2.666666667x + x2 = 0 + 8.333333333

Combine like terms: -8.333333333 + 8.333333333 = 0.000000000
0.000000000 + -2.666666667x + x2 = 0 + 8.333333333
-2.666666667x + x2 = 0 + 8.333333333

Combine like terms: 0 + 8.333333333 = 8.333333333
-2.666666667x + x2 = 8.333333333

The x term is -2.666666667x.  Take half its coefficient (-1.333333334).
Square it (1.777777780) and add it to both sides.

Add '1.777777780' to each side of the equation.
-2.666666667x + 1.777777780 + x2 = 8.333333333 + 1.777777780

Reorder the terms:
1.777777780 + -2.666666667x + x2 = 8.333333333 + 1.777777780

Combine like terms: 8.333333333 + 1.777777780 = 10.111111113
1.777777780 + -2.666666667x + x2 = 10.111111113

Factor a perfect square on the left side:
(x + -1.333333334)(x + -1.333333334) = 10.111111113

Calculate the square root of the right side: 3.179797338

Break this problem into two subproblems by setting 
(x + -1.333333334) equal to 3.179797338 and -3.179797338.

Subproblem 1

x + -1.333333334 = 3.179797338 Simplifying x + -1.333333334 = 3.179797338 Reorder the terms: -1.333333334 + x = 3.179797338 Solving -1.333333334 + x = 3.179797338 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.333333334' to each side of the equation. -1.333333334 + 1.333333334 + x = 3.179797338 + 1.333333334 Combine like terms: -1.333333334 + 1.333333334 = 0.000000000 0.000000000 + x = 3.179797338 + 1.333333334 x = 3.179797338 + 1.333333334 Combine like terms: 3.179797338 + 1.333333334 = 4.513130672 x = 4.513130672 Simplifying x = 4.513130672

Subproblem 2

x + -1.333333334 = -3.179797338 Simplifying x + -1.333333334 = -3.179797338 Reorder the terms: -1.333333334 + x = -3.179797338 Solving -1.333333334 + x = -3.179797338 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.333333334' to each side of the equation. -1.333333334 + 1.333333334 + x = -3.179797338 + 1.333333334 Combine like terms: -1.333333334 + 1.333333334 = 0.000000000 0.000000000 + x = -3.179797338 + 1.333333334 x = -3.179797338 + 1.333333334 Combine like terms: -3.179797338 + 1.333333334 = -1.846464004 x = -1.846464004 Simplifying x = -1.846464004

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.513130672, -1.846464004}

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