(n+4)(n-5)=81

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Solution for (n+4)(n-5)=81 equation:


Simplifying
(n + 4)(n + -5) = 81

Reorder the terms:
(4 + n)(n + -5) = 81

Reorder the terms:
(4 + n)(-5 + n) = 81

Multiply (4 + n) * (-5 + n)
(4(-5 + n) + n(-5 + n)) = 81
((-5 * 4 + n * 4) + n(-5 + n)) = 81
((-20 + 4n) + n(-5 + n)) = 81
(-20 + 4n + (-5 * n + n * n)) = 81
(-20 + 4n + (-5n + n2)) = 81

Combine like terms: 4n + -5n = -1n
(-20 + -1n + n2) = 81

Solving
-20 + -1n + n2 = 81

Solving for variable 'n'.

Reorder the terms:
-20 + -81 + -1n + n2 = 81 + -81

Combine like terms: -20 + -81 = -101
-101 + -1n + n2 = 81 + -81

Combine like terms: 81 + -81 = 0
-101 + -1n + n2 = 0

Begin completing the square.

Move the constant term to the right:

Add '101' to each side of the equation.
-101 + -1n + 101 + n2 = 0 + 101

Reorder the terms:
-101 + 101 + -1n + n2 = 0 + 101

Combine like terms: -101 + 101 = 0
0 + -1n + n2 = 0 + 101
-1n + n2 = 0 + 101

Combine like terms: 0 + 101 = 101
-1n + n2 = 101

The n term is -1n.  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.
-1n + 0.25 + n2 = 101 + 0.25

Reorder the terms:
0.25 + -1n + n2 = 101 + 0.25

Combine like terms: 101 + 0.25 = 101.25
0.25 + -1n + n2 = 101.25

Factor a perfect square on the left side:
(n + -0.5)(n + -0.5) = 101.25

Calculate the square root of the right side: 10.062305899

Break this problem into two subproblems by setting 
(n + -0.5) equal to 10.062305899 and -10.062305899.

Subproblem 1

n + -0.5 = 10.062305899 Simplifying n + -0.5 = 10.062305899 Reorder the terms: -0.5 + n = 10.062305899 Solving -0.5 + n = 10.062305899 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 = 10.062305899 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + n = 10.062305899 + 0.5 n = 10.062305899 + 0.5 Combine like terms: 10.062305899 + 0.5 = 10.562305899 n = 10.562305899 Simplifying n = 10.562305899

Subproblem 2

n + -0.5 = -10.062305899 Simplifying n + -0.5 = -10.062305899 Reorder the terms: -0.5 + n = -10.062305899 Solving -0.5 + n = -10.062305899 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 = -10.062305899 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + n = -10.062305899 + 0.5 n = -10.062305899 + 0.5 Combine like terms: -10.062305899 + 0.5 = -9.562305899 n = -9.562305899 Simplifying n = -9.562305899

Solution

The solution to the problem is based on the solutions from the subproblems. n = {10.562305899, -9.562305899}

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