-x^2+4x+15=0

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Solution for -x^2+4x+15=0 equation: 


Simplifying
-1x2 + 4x + 15 = 0

Reorder the terms:
15 + 4x + -1x2 = 0

Solving
15 + 4x + -1x2 = 0

Solving for variable 'x'.

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

Divide each side by '-1'.
-15 + -4x + x2 = 0

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + -4x + 15 + x2 = 0 + 15

Reorder the terms:
-15 + 15 + -4x + x2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + -4x + x2 = 0 + 15
-4x + x2 = 0 + 15

Combine like terms: 0 + 15 = 15
-4x + x2 = 15

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

Add '4' to each side of the equation.
-4x + 4 + x2 = 15 + 4

Reorder the terms:
4 + -4x + x2 = 15 + 4

Combine like terms: 15 + 4 = 19
4 + -4x + x2 = 19

Factor a perfect square on the left side:
(x + -2)(x + -2) = 19

Calculate the square root of the right side: 4.358898944

Break this problem into two subproblems by setting 
(x + -2) equal to 4.358898944 and -4.358898944.


Subproblem 1
x + -2 = 4.358898944

Simplifying
x + -2 = 4.358898944

Reorder the terms:
-2 + x = 4.358898944

Solving
-2 + x = 4.358898944

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '2' to each side of the equation.
-2 + 2 + x = 4.358898944 + 2

Combine like terms: -2 + 2 = 0
0 + x = 4.358898944 + 2
x = 4.358898944 + 2

Combine like terms: 4.358898944 + 2 = 6.358898944
x = 6.358898944

Simplifying
x = 6.358898944


Subproblem 2
x + -2 = -4.358898944

Simplifying
x + -2 = -4.358898944

Reorder the terms:
-2 + x = -4.358898944

Solving
-2 + x = -4.358898944

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '2' to each side of the equation.
-2 + 2 + x = -4.358898944 + 2

Combine like terms: -2 + 2 = 0
0 + x = -4.358898944 + 2
x = -4.358898944 + 2

Combine like terms: -4.358898944 + 2 = -2.358898944
x = -2.358898944

Simplifying
x = -2.358898944


Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {6.358898944, -2.358898944}

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