-a^2-4a+9=0

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Solution for -a^2-4a+9=0 equation:


Simplifying
-1a2 + -4a + 9 = 0

Reorder the terms:
9 + -4a + -1a2 = 0

Solving
9 + -4a + -1a2 = 0

Solving for variable 'a'.

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-9 + 4a + a2 = 0

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + 4a + 9 + a2 = 0 + 9

Reorder the terms:
-9 + 9 + 4a + a2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + 4a + a2 = 0 + 9
4a + a2 = 0 + 9

Combine like terms: 0 + 9 = 9
4a + a2 = 9

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

Add '4' to each side of the equation.
4a + 4 + a2 = 9 + 4

Reorder the terms:
4 + 4a + a2 = 9 + 4

Combine like terms: 9 + 4 = 13
4 + 4a + a2 = 13

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

Calculate the square root of the right side: 3.605551275

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

Subproblem 1

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

Subproblem 2

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

Solution

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

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