2x^2+5x-400=0

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Solution for 2x^2+5x-400=0 equation:


Simplifying
2x2 + 5x + -400 = 0

Reorder the terms:
-400 + 5x + 2x2 = 0

Solving
-400 + 5x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
-200 + 2.5x + x2 = 0

Move the constant term to the right:

Add '200' to each side of the equation.
-200 + 2.5x + 200 + x2 = 0 + 200

Reorder the terms:
-200 + 200 + 2.5x + x2 = 0 + 200

Combine like terms: -200 + 200 = 0
0 + 2.5x + x2 = 0 + 200
2.5x + x2 = 0 + 200

Combine like terms: 0 + 200 = 200
2.5x + x2 = 200

The x term is 2.5x.  Take half its coefficient (1.25).
Square it (1.5625) and add it to both sides.

Add '1.5625' to each side of the equation.
2.5x + 1.5625 + x2 = 200 + 1.5625

Reorder the terms:
1.5625 + 2.5x + x2 = 200 + 1.5625

Combine like terms: 200 + 1.5625 = 201.5625
1.5625 + 2.5x + x2 = 201.5625

Factor a perfect square on the left side:
(x + 1.25)(x + 1.25) = 201.5625

Calculate the square root of the right side: 14.197270865

Break this problem into two subproblems by setting 
(x + 1.25) equal to 14.197270865 and -14.197270865.

Subproblem 1

x + 1.25 = 14.197270865 Simplifying x + 1.25 = 14.197270865 Reorder the terms: 1.25 + x = 14.197270865 Solving 1.25 + x = 14.197270865 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.25' to each side of the equation. 1.25 + -1.25 + x = 14.197270865 + -1.25 Combine like terms: 1.25 + -1.25 = 0.00 0.00 + x = 14.197270865 + -1.25 x = 14.197270865 + -1.25 Combine like terms: 14.197270865 + -1.25 = 12.947270865 x = 12.947270865 Simplifying x = 12.947270865

Subproblem 2

x + 1.25 = -14.197270865 Simplifying x + 1.25 = -14.197270865 Reorder the terms: 1.25 + x = -14.197270865 Solving 1.25 + x = -14.197270865 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.25' to each side of the equation. 1.25 + -1.25 + x = -14.197270865 + -1.25 Combine like terms: 1.25 + -1.25 = 0.00 0.00 + x = -14.197270865 + -1.25 x = -14.197270865 + -1.25 Combine like terms: -14.197270865 + -1.25 = -15.447270865 x = -15.447270865 Simplifying x = -15.447270865

Solution

The solution to the problem is based on the solutions from the subproblems. x = {12.947270865, -15.447270865}

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