u^2-9u-20=0

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Solution for u^2-9u-20=0 equation:


Simplifying
u2 + -9u + -20 = 0

Reorder the terms:
-20 + -9u + u2 = 0

Solving
-20 + -9u + u2 = 0

Solving for variable 'u'.

Begin completing the square.

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + -9u + 20 + u2 = 0 + 20

Reorder the terms:
-20 + 20 + -9u + u2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + -9u + u2 = 0 + 20
-9u + u2 = 0 + 20

Combine like terms: 0 + 20 = 20
-9u + u2 = 20

The u term is -9u.  Take half its coefficient (-4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
-9u + 20.25 + u2 = 20 + 20.25

Reorder the terms:
20.25 + -9u + u2 = 20 + 20.25

Combine like terms: 20 + 20.25 = 40.25
20.25 + -9u + u2 = 40.25

Factor a perfect square on the left side:
(u + -4.5)(u + -4.5) = 40.25

Calculate the square root of the right side: 6.34428877

Break this problem into two subproblems by setting 
(u + -4.5) equal to 6.34428877 and -6.34428877.

Subproblem 1

u + -4.5 = 6.34428877 Simplifying u + -4.5 = 6.34428877 Reorder the terms: -4.5 + u = 6.34428877 Solving -4.5 + u = 6.34428877 Solving for variable 'u'. Move all terms containing u to the left, all other terms to the right. Add '4.5' to each side of the equation. -4.5 + 4.5 + u = 6.34428877 + 4.5 Combine like terms: -4.5 + 4.5 = 0.0 0.0 + u = 6.34428877 + 4.5 u = 6.34428877 + 4.5 Combine like terms: 6.34428877 + 4.5 = 10.84428877 u = 10.84428877 Simplifying u = 10.84428877

Subproblem 2

u + -4.5 = -6.34428877 Simplifying u + -4.5 = -6.34428877 Reorder the terms: -4.5 + u = -6.34428877 Solving -4.5 + u = -6.34428877 Solving for variable 'u'. Move all terms containing u to the left, all other terms to the right. Add '4.5' to each side of the equation. -4.5 + 4.5 + u = -6.34428877 + 4.5 Combine like terms: -4.5 + 4.5 = 0.0 0.0 + u = -6.34428877 + 4.5 u = -6.34428877 + 4.5 Combine like terms: -6.34428877 + 4.5 = -1.84428877 u = -1.84428877 Simplifying u = -1.84428877

Solution

The solution to the problem is based on the solutions from the subproblems. u = {10.84428877, -1.84428877}

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