x^2+x-398=0

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Solution for x^2+x-398=0 equation:


Simplifying
x2 + x + -398 = 0

Reorder the terms:
-398 + x + x2 = 0

Solving
-398 + x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '398' to each side of the equation.
-398 + x + 398 + x2 = 0 + 398

Reorder the terms:
-398 + 398 + x + x2 = 0 + 398

Combine like terms: -398 + 398 = 0
0 + x + x2 = 0 + 398
x + x2 = 0 + 398

Combine like terms: 0 + 398 = 398
x + x2 = 398

The x term is x.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
x + 0.25 + x2 = 398 + 0.25

Reorder the terms:
0.25 + x + x2 = 398 + 0.25

Combine like terms: 398 + 0.25 = 398.25
0.25 + x + x2 = 398.25

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = 398.25

Calculate the square root of the right side: 19.956202043

Break this problem into two subproblems by setting 
(x + 0.5) equal to 19.956202043 and -19.956202043.

Subproblem 1

x + 0.5 = 19.956202043 Simplifying x + 0.5 = 19.956202043 Reorder the terms: 0.5 + x = 19.956202043 Solving 0.5 + x = 19.956202043 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = 19.956202043 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = 19.956202043 + -0.5 x = 19.956202043 + -0.5 Combine like terms: 19.956202043 + -0.5 = 19.456202043 x = 19.456202043 Simplifying x = 19.456202043

Subproblem 2

x + 0.5 = -19.956202043 Simplifying x + 0.5 = -19.956202043 Reorder the terms: 0.5 + x = -19.956202043 Solving 0.5 + x = -19.956202043 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = -19.956202043 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = -19.956202043 + -0.5 x = -19.956202043 + -0.5 Combine like terms: -19.956202043 + -0.5 = -20.456202043 x = -20.456202043 Simplifying x = -20.456202043

Solution

The solution to the problem is based on the solutions from the subproblems. x = {19.456202043, -20.456202043}

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