(7-3x)(x+4)=18

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Solution for (7-3x)(x+4)=18 equation:


Simplifying
(7 + -3x)(x + 4) = 18

Reorder the terms:
(7 + -3x)(4 + x) = 18

Multiply (7 + -3x) * (4 + x)
(7(4 + x) + -3x * (4 + x)) = 18
((4 * 7 + x * 7) + -3x * (4 + x)) = 18
((28 + 7x) + -3x * (4 + x)) = 18
(28 + 7x + (4 * -3x + x * -3x)) = 18
(28 + 7x + (-12x + -3x2)) = 18

Combine like terms: 7x + -12x = -5x
(28 + -5x + -3x2) = 18

Solving
28 + -5x + -3x2 = 18

Solving for variable 'x'.

Reorder the terms:
28 + -18 + -5x + -3x2 = 18 + -18

Combine like terms: 28 + -18 = 10
10 + -5x + -3x2 = 18 + -18

Combine like terms: 18 + -18 = 0
10 + -5x + -3x2 = 0

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

Divide each side by '-3'.
-3.333333333 + 1.666666667x + x2 = 0

Move the constant term to the right:

Add '3.333333333' to each side of the equation.
-3.333333333 + 1.666666667x + 3.333333333 + x2 = 0 + 3.333333333

Reorder the terms:
-3.333333333 + 3.333333333 + 1.666666667x + x2 = 0 + 3.333333333

Combine like terms: -3.333333333 + 3.333333333 = 0.000000000
0.000000000 + 1.666666667x + x2 = 0 + 3.333333333
1.666666667x + x2 = 0 + 3.333333333

Combine like terms: 0 + 3.333333333 = 3.333333333
1.666666667x + x2 = 3.333333333

The x term is 1.666666667x.  Take half its coefficient (0.8333333335).
Square it (0.6944444447) and add it to both sides.

Add '0.6944444447' to each side of the equation.
1.666666667x + 0.6944444447 + x2 = 3.333333333 + 0.6944444447

Reorder the terms:
0.6944444447 + 1.666666667x + x2 = 3.333333333 + 0.6944444447

Combine like terms: 3.333333333 + 0.6944444447 = 4.0277777777
0.6944444447 + 1.666666667x + x2 = 4.0277777777

Factor a perfect square on the left side:
(x + 0.8333333335)(x + 0.8333333335) = 4.0277777777

Calculate the square root of the right side: 2.00693243

Break this problem into two subproblems by setting 
(x + 0.8333333335) equal to 2.00693243 and -2.00693243.

Subproblem 1

x + 0.8333333335 = 2.00693243 Simplifying x + 0.8333333335 = 2.00693243 Reorder the terms: 0.8333333335 + x = 2.00693243 Solving 0.8333333335 + x = 2.00693243 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.8333333335' to each side of the equation. 0.8333333335 + -0.8333333335 + x = 2.00693243 + -0.8333333335 Combine like terms: 0.8333333335 + -0.8333333335 = 0.0000000000 0.0000000000 + x = 2.00693243 + -0.8333333335 x = 2.00693243 + -0.8333333335 Combine like terms: 2.00693243 + -0.8333333335 = 1.1735990965 x = 1.1735990965 Simplifying x = 1.1735990965

Subproblem 2

x + 0.8333333335 = -2.00693243 Simplifying x + 0.8333333335 = -2.00693243 Reorder the terms: 0.8333333335 + x = -2.00693243 Solving 0.8333333335 + x = -2.00693243 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.8333333335' to each side of the equation. 0.8333333335 + -0.8333333335 + x = -2.00693243 + -0.8333333335 Combine like terms: 0.8333333335 + -0.8333333335 = 0.0000000000 0.0000000000 + x = -2.00693243 + -0.8333333335 x = -2.00693243 + -0.8333333335 Combine like terms: -2.00693243 + -0.8333333335 = -2.8402657635 x = -2.8402657635 Simplifying x = -2.8402657635

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.1735990965, -2.8402657635}

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