u^2-u-8=0

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Solution for u^2-u-8=0 equation:


Simplifying
u2 + -1u + -8 = 0

Reorder the terms:
-8 + -1u + u2 = 0

Solving
-8 + -1u + u2 = 0

Solving for variable 'u'.

Begin completing the square.

Move the constant term to the right:

Add '8' to each side of the equation.
-8 + -1u + 8 + u2 = 0 + 8

Reorder the terms:
-8 + 8 + -1u + u2 = 0 + 8

Combine like terms: -8 + 8 = 0
0 + -1u + u2 = 0 + 8
-1u + u2 = 0 + 8

Combine like terms: 0 + 8 = 8
-1u + u2 = 8

The u term is -1u.  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.
-1u + 0.25 + u2 = 8 + 0.25

Reorder the terms:
0.25 + -1u + u2 = 8 + 0.25

Combine like terms: 8 + 0.25 = 8.25
0.25 + -1u + u2 = 8.25

Factor a perfect square on the left side:
(u + -0.5)(u + -0.5) = 8.25

Calculate the square root of the right side: 2.872281323

Break this problem into two subproblems by setting 
(u + -0.5) equal to 2.872281323 and -2.872281323.

Subproblem 1

u + -0.5 = 2.872281323 Simplifying u + -0.5 = 2.872281323 Reorder the terms: -0.5 + u = 2.872281323 Solving -0.5 + u = 2.872281323 Solving for variable 'u'. Move all terms containing u to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + u = 2.872281323 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + u = 2.872281323 + 0.5 u = 2.872281323 + 0.5 Combine like terms: 2.872281323 + 0.5 = 3.372281323 u = 3.372281323 Simplifying u = 3.372281323

Subproblem 2

u + -0.5 = -2.872281323 Simplifying u + -0.5 = -2.872281323 Reorder the terms: -0.5 + u = -2.872281323 Solving -0.5 + u = -2.872281323 Solving for variable 'u'. Move all terms containing u to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + u = -2.872281323 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + u = -2.872281323 + 0.5 u = -2.872281323 + 0.5 Combine like terms: -2.872281323 + 0.5 = -2.372281323 u = -2.372281323 Simplifying u = -2.372281323

Solution

The solution to the problem is based on the solutions from the subproblems. u = {3.372281323, -2.372281323}

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