u^2+4u=9

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Solution for u^2+4u=9 equation:


Simplifying
u2 + 4u = 9

Reorder the terms:
4u + u2 = 9

Solving
4u + u2 = 9

Solving for variable 'u'.

Reorder the terms:
-9 + 4u + u2 = 9 + -9

Combine like terms: 9 + -9 = 0
-9 + 4u + u2 = 0

Begin completing the square.

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + 4u + 9 + u2 = 0 + 9

Reorder the terms:
-9 + 9 + 4u + u2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + 4u + u2 = 0 + 9
4u + u2 = 0 + 9

Combine like terms: 0 + 9 = 9
4u + u2 = 9

The u term is 4u.  Take half its coefficient (2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
4u + 4 + u2 = 9 + 4

Reorder the terms:
4 + 4u + u2 = 9 + 4

Combine like terms: 9 + 4 = 13
4 + 4u + u2 = 13

Factor a perfect square on the left side:
(u + 2)(u + 2) = 13

Calculate the square root of the right side: 3.605551275

Break this problem into two subproblems by setting 
(u + 2) equal to 3.605551275 and -3.605551275.

Subproblem 1

u + 2 = 3.605551275 Simplifying u + 2 = 3.605551275 Reorder the terms: 2 + u = 3.605551275 Solving 2 + u = 3.605551275 Solving for variable 'u'. Move all terms containing u to the left, all other terms to the right. Add '-2' to each side of the equation. 2 + -2 + u = 3.605551275 + -2 Combine like terms: 2 + -2 = 0 0 + u = 3.605551275 + -2 u = 3.605551275 + -2 Combine like terms: 3.605551275 + -2 = 1.605551275 u = 1.605551275 Simplifying u = 1.605551275

Subproblem 2

u + 2 = -3.605551275 Simplifying u + 2 = -3.605551275 Reorder the terms: 2 + u = -3.605551275 Solving 2 + u = -3.605551275 Solving for variable 'u'. Move all terms containing u to the left, all other terms to the right. Add '-2' to each side of the equation. 2 + -2 + u = -3.605551275 + -2 Combine like terms: 2 + -2 = 0 0 + u = -3.605551275 + -2 u = -3.605551275 + -2 Combine like terms: -3.605551275 + -2 = -5.605551275 u = -5.605551275 Simplifying u = -5.605551275

Solution

The solution to the problem is based on the solutions from the subproblems. u = {1.605551275, -5.605551275}

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