7x^2-12x-28=0

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Solution for 7x^2-12x-28=0 equation:


Simplifying
7x2 + -12x + -28 = 0

Reorder the terms:
-28 + -12x + 7x2 = 0

Solving
-28 + -12x + 7x2 = 0

Solving for variable 'x'.

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

Divide each side by '7'.
-4 + -1.714285714x + x2 = 0

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + -1.714285714x + 4 + x2 = 0 + 4

Reorder the terms:
-4 + 4 + -1.714285714x + x2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -1.714285714x + x2 = 0 + 4
-1.714285714x + x2 = 0 + 4

Combine like terms: 0 + 4 = 4
-1.714285714x + x2 = 4

The x term is -1.714285714x.  Take half its coefficient (-0.857142857).
Square it (0.7346938773) and add it to both sides.

Add '0.7346938773' to each side of the equation.
-1.714285714x + 0.7346938773 + x2 = 4 + 0.7346938773

Reorder the terms:
0.7346938773 + -1.714285714x + x2 = 4 + 0.7346938773

Combine like terms: 4 + 0.7346938773 = 4.7346938773
0.7346938773 + -1.714285714x + x2 = 4.7346938773

Factor a perfect square on the left side:
(x + -0.857142857)(x + -0.857142857) = 4.7346938773

Calculate the square root of the right side: 2.175935173

Break this problem into two subproblems by setting 
(x + -0.857142857) equal to 2.175935173 and -2.175935173.

Subproblem 1

x + -0.857142857 = 2.175935173 Simplifying x + -0.857142857 = 2.175935173 Reorder the terms: -0.857142857 + x = 2.175935173 Solving -0.857142857 + x = 2.175935173 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.857142857' to each side of the equation. -0.857142857 + 0.857142857 + x = 2.175935173 + 0.857142857 Combine like terms: -0.857142857 + 0.857142857 = 0.000000000 0.000000000 + x = 2.175935173 + 0.857142857 x = 2.175935173 + 0.857142857 Combine like terms: 2.175935173 + 0.857142857 = 3.03307803 x = 3.03307803 Simplifying x = 3.03307803

Subproblem 2

x + -0.857142857 = -2.175935173 Simplifying x + -0.857142857 = -2.175935173 Reorder the terms: -0.857142857 + x = -2.175935173 Solving -0.857142857 + x = -2.175935173 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.857142857' to each side of the equation. -0.857142857 + 0.857142857 + x = -2.175935173 + 0.857142857 Combine like terms: -0.857142857 + 0.857142857 = 0.000000000 0.000000000 + x = -2.175935173 + 0.857142857 x = -2.175935173 + 0.857142857 Combine like terms: -2.175935173 + 0.857142857 = -1.318792316 x = -1.318792316 Simplifying x = -1.318792316

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.03307803, -1.318792316}

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