7x^2-20x-140=0

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Solution for 7x^2-20x-140=0 equation:


Simplifying
7x2 + -20x + -140 = 0

Reorder the terms:
-140 + -20x + 7x2 = 0

Solving
-140 + -20x + 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'.
-20 + -2.857142857x + x2 = 0

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + -2.857142857x + 20 + x2 = 0 + 20

Reorder the terms:
-20 + 20 + -2.857142857x + x2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + -2.857142857x + x2 = 0 + 20
-2.857142857x + x2 = 0 + 20

Combine like terms: 0 + 20 = 20
-2.857142857x + x2 = 20

The x term is -2.857142857x.  Take half its coefficient (-1.428571429).
Square it (2.040816328) and add it to both sides.

Add '2.040816328' to each side of the equation.
-2.857142857x + 2.040816328 + x2 = 20 + 2.040816328

Reorder the terms:
2.040816328 + -2.857142857x + x2 = 20 + 2.040816328

Combine like terms: 20 + 2.040816328 = 22.040816328
2.040816328 + -2.857142857x + x2 = 22.040816328

Factor a perfect square on the left side:
(x + -1.428571429)(x + -1.428571429) = 22.040816328

Calculate the square root of the right side: 4.694764779

Break this problem into two subproblems by setting 
(x + -1.428571429) equal to 4.694764779 and -4.694764779.

Subproblem 1

x + -1.428571429 = 4.694764779 Simplifying x + -1.428571429 = 4.694764779 Reorder the terms: -1.428571429 + x = 4.694764779 Solving -1.428571429 + x = 4.694764779 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.428571429' to each side of the equation. -1.428571429 + 1.428571429 + x = 4.694764779 + 1.428571429 Combine like terms: -1.428571429 + 1.428571429 = 0.000000000 0.000000000 + x = 4.694764779 + 1.428571429 x = 4.694764779 + 1.428571429 Combine like terms: 4.694764779 + 1.428571429 = 6.123336208 x = 6.123336208 Simplifying x = 6.123336208

Subproblem 2

x + -1.428571429 = -4.694764779 Simplifying x + -1.428571429 = -4.694764779 Reorder the terms: -1.428571429 + x = -4.694764779 Solving -1.428571429 + x = -4.694764779 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.428571429' to each side of the equation. -1.428571429 + 1.428571429 + x = -4.694764779 + 1.428571429 Combine like terms: -1.428571429 + 1.428571429 = 0.000000000 0.000000000 + x = -4.694764779 + 1.428571429 x = -4.694764779 + 1.428571429 Combine like terms: -4.694764779 + 1.428571429 = -3.26619335 x = -3.26619335 Simplifying x = -3.26619335

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.123336208, -3.26619335}

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