n^2+n-81=0

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Solution for n^2+n-81=0 equation:


Simplifying
n2 + n + -81 = 0

Reorder the terms:
-81 + n + n2 = 0

Solving
-81 + n + n2 = 0

Solving for variable 'n'.

Begin completing the square.

Move the constant term to the right:

Add '81' to each side of the equation.
-81 + n + 81 + n2 = 0 + 81

Reorder the terms:
-81 + 81 + n + n2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + n + n2 = 0 + 81
n + n2 = 0 + 81

Combine like terms: 0 + 81 = 81
n + n2 = 81

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 = 81 + 0.25

Reorder the terms:
0.25 + n + n2 = 81 + 0.25

Combine like terms: 81 + 0.25 = 81.25
0.25 + n + n2 = 81.25

Factor a perfect square on the left side:
(n + 0.5)(n + 0.5) = 81.25

Calculate the square root of the right side: 9.013878189

Break this problem into two subproblems by setting 
(n + 0.5) equal to 9.013878189 and -9.013878189.

Subproblem 1

n + 0.5 = 9.013878189 Simplifying n + 0.5 = 9.013878189 Reorder the terms: 0.5 + n = 9.013878189 Solving 0.5 + n = 9.013878189 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 = 9.013878189 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + n = 9.013878189 + -0.5 n = 9.013878189 + -0.5 Combine like terms: 9.013878189 + -0.5 = 8.513878189 n = 8.513878189 Simplifying n = 8.513878189

Subproblem 2

n + 0.5 = -9.013878189 Simplifying n + 0.5 = -9.013878189 Reorder the terms: 0.5 + n = -9.013878189 Solving 0.5 + n = -9.013878189 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 = -9.013878189 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + n = -9.013878189 + -0.5 n = -9.013878189 + -0.5 Combine like terms: -9.013878189 + -0.5 = -9.513878189 n = -9.513878189 Simplifying n = -9.513878189

Solution

The solution to the problem is based on the solutions from the subproblems. n = {8.513878189, -9.513878189}

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