7x^2-4x-400=0

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Solution for 7x^2-4x-400=0 equation:


Simplifying
7x2 + -4x + -400 = 0

Reorder the terms:
-400 + -4x + 7x2 = 0

Solving
-400 + -4x + 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'.
-57.14285714 + -0.5714285714x + x2 = 0

Move the constant term to the right:

Add '57.14285714' to each side of the equation.
-57.14285714 + -0.5714285714x + 57.14285714 + x2 = 0 + 57.14285714

Reorder the terms:
-57.14285714 + 57.14285714 + -0.5714285714x + x2 = 0 + 57.14285714

Combine like terms: -57.14285714 + 57.14285714 = 0.00000000
0.00000000 + -0.5714285714x + x2 = 0 + 57.14285714
-0.5714285714x + x2 = 0 + 57.14285714

Combine like terms: 0 + 57.14285714 = 57.14285714
-0.5714285714x + x2 = 57.14285714

The x term is -0.5714285714x.  Take half its coefficient (-0.2857142857).
Square it (0.08163265305) and add it to both sides.

Add '0.08163265305' to each side of the equation.
-0.5714285714x + 0.08163265305 + x2 = 57.14285714 + 0.08163265305

Reorder the terms:
0.08163265305 + -0.5714285714x + x2 = 57.14285714 + 0.08163265305

Combine like terms: 57.14285714 + 0.08163265305 = 57.22448979305
0.08163265305 + -0.5714285714x + x2 = 57.22448979305

Factor a perfect square on the left side:
(x + -0.2857142857)(x + -0.2857142857) = 57.22448979305

Calculate the square root of the right side: 7.564687025

Break this problem into two subproblems by setting 
(x + -0.2857142857) equal to 7.564687025 and -7.564687025.

Subproblem 1

x + -0.2857142857 = 7.564687025 Simplifying x + -0.2857142857 = 7.564687025 Reorder the terms: -0.2857142857 + x = 7.564687025 Solving -0.2857142857 + x = 7.564687025 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.2857142857' to each side of the equation. -0.2857142857 + 0.2857142857 + x = 7.564687025 + 0.2857142857 Combine like terms: -0.2857142857 + 0.2857142857 = 0.0000000000 0.0000000000 + x = 7.564687025 + 0.2857142857 x = 7.564687025 + 0.2857142857 Combine like terms: 7.564687025 + 0.2857142857 = 7.8504013107 x = 7.8504013107 Simplifying x = 7.8504013107

Subproblem 2

x + -0.2857142857 = -7.564687025 Simplifying x + -0.2857142857 = -7.564687025 Reorder the terms: -0.2857142857 + x = -7.564687025 Solving -0.2857142857 + x = -7.564687025 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.2857142857' to each side of the equation. -0.2857142857 + 0.2857142857 + x = -7.564687025 + 0.2857142857 Combine like terms: -0.2857142857 + 0.2857142857 = 0.0000000000 0.0000000000 + x = -7.564687025 + 0.2857142857 x = -7.564687025 + 0.2857142857 Combine like terms: -7.564687025 + 0.2857142857 = -7.2789727393 x = -7.2789727393 Simplifying x = -7.2789727393

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.8504013107, -7.2789727393}

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