n^2+n-400=0

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Solution for n^2+n-400=0 equation:


Simplifying
n2 + n + -400 = 0

Reorder the terms:
-400 + n + n2 = 0

Solving
-400 + n + n2 = 0

Solving for variable 'n'.

Begin completing the square.

Move the constant term to the right:

Add '400' to each side of the equation.
-400 + n + 400 + n2 = 0 + 400

Reorder the terms:
-400 + 400 + n + n2 = 0 + 400

Combine like terms: -400 + 400 = 0
0 + n + n2 = 0 + 400
n + n2 = 0 + 400

Combine like terms: 0 + 400 = 400
n + n2 = 400

The n term is n.  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.
n + 0.25 + n2 = 400 + 0.25

Reorder the terms:
0.25 + n + n2 = 400 + 0.25

Combine like terms: 400 + 0.25 = 400.25
0.25 + n + n2 = 400.25

Factor a perfect square on the left side:
(n + 0.5)(n + 0.5) = 400.25

Calculate the square root of the right side: 20.006249024

Break this problem into two subproblems by setting 
(n + 0.5) equal to 20.006249024 and -20.006249024.

Subproblem 1

n + 0.5 = 20.006249024 Simplifying n + 0.5 = 20.006249024 Reorder the terms: 0.5 + n = 20.006249024 Solving 0.5 + n = 20.006249024 Solving for variable 'n'. Move all terms containing n to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + n = 20.006249024 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + n = 20.006249024 + -0.5 n = 20.006249024 + -0.5 Combine like terms: 20.006249024 + -0.5 = 19.506249024 n = 19.506249024 Simplifying n = 19.506249024

Subproblem 2

n + 0.5 = -20.006249024 Simplifying n + 0.5 = -20.006249024 Reorder the terms: 0.5 + n = -20.006249024 Solving 0.5 + n = -20.006249024 Solving for variable 'n'. Move all terms containing n to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + n = -20.006249024 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + n = -20.006249024 + -0.5 n = -20.006249024 + -0.5 Combine like terms: -20.006249024 + -0.5 = -20.506249024 n = -20.506249024 Simplifying n = -20.506249024

Solution

The solution to the problem is based on the solutions from the subproblems. n = {19.506249024, -20.506249024}

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