u^2-6u-9=0

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Solution for u^2-6u-9=0 equation:


Simplifying
u2 + -6u + -9 = 0

Reorder the terms:
-9 + -6u + u2 = 0

Solving
-9 + -6u + u2 = 0

Solving for variable 'u'.

Begin completing the square.

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + -6u + 9 + u2 = 0 + 9

Reorder the terms:
-9 + 9 + -6u + u2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + -6u + u2 = 0 + 9
-6u + u2 = 0 + 9

Combine like terms: 0 + 9 = 9
-6u + u2 = 9

The u term is -6u.  Take half its coefficient (-3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
-6u + 9 + u2 = 9 + 9

Reorder the terms:
9 + -6u + u2 = 9 + 9

Combine like terms: 9 + 9 = 18
9 + -6u + u2 = 18

Factor a perfect square on the left side:
(u + -3)(u + -3) = 18

Calculate the square root of the right side: 4.242640687

Break this problem into two subproblems by setting 
(u + -3) equal to 4.242640687 and -4.242640687.

Subproblem 1

u + -3 = 4.242640687 Simplifying u + -3 = 4.242640687 Reorder the terms: -3 + u = 4.242640687 Solving -3 + u = 4.242640687 Solving for variable 'u'. Move all terms containing u to the left, all other terms to the right. Add '3' to each side of the equation. -3 + 3 + u = 4.242640687 + 3 Combine like terms: -3 + 3 = 0 0 + u = 4.242640687 + 3 u = 4.242640687 + 3 Combine like terms: 4.242640687 + 3 = 7.242640687 u = 7.242640687 Simplifying u = 7.242640687

Subproblem 2

u + -3 = -4.242640687 Simplifying u + -3 = -4.242640687 Reorder the terms: -3 + u = -4.242640687 Solving -3 + u = -4.242640687 Solving for variable 'u'. Move all terms containing u to the left, all other terms to the right. Add '3' to each side of the equation. -3 + 3 + u = -4.242640687 + 3 Combine like terms: -3 + 3 = 0 0 + u = -4.242640687 + 3 u = -4.242640687 + 3 Combine like terms: -4.242640687 + 3 = -1.242640687 u = -1.242640687 Simplifying u = -1.242640687

Solution

The solution to the problem is based on the solutions from the subproblems. u = {7.242640687, -1.242640687}

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