x^2+2x+8=20

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Solution for x^2+2x+8=20 equation:


Simplifying
x2 + 2x + 8 = 20

Reorder the terms:
8 + 2x + x2 = 20

Solving
8 + 2x + x2 = 20

Solving for variable 'x'.

Reorder the terms:
8 + -20 + 2x + x2 = 20 + -20

Combine like terms: 8 + -20 = -12
-12 + 2x + x2 = 20 + -20

Combine like terms: 20 + -20 = 0
-12 + 2x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '12' to each side of the equation.
-12 + 2x + 12 + x2 = 0 + 12

Reorder the terms:
-12 + 12 + 2x + x2 = 0 + 12

Combine like terms: -12 + 12 = 0
0 + 2x + x2 = 0 + 12
2x + x2 = 0 + 12

Combine like terms: 0 + 12 = 12
2x + x2 = 12

The x term is 2x.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2x + 1 + x2 = 12 + 1

Reorder the terms:
1 + 2x + x2 = 12 + 1

Combine like terms: 12 + 1 = 13
1 + 2x + x2 = 13

Factor a perfect square on the left side:
(x + 1)(x + 1) = 13

Calculate the square root of the right side: 3.605551275

Break this problem into two subproblems by setting 
(x + 1) equal to 3.605551275 and -3.605551275.

Subproblem 1

x + 1 = 3.605551275 Simplifying x + 1 = 3.605551275 Reorder the terms: 1 + x = 3.605551275 Solving 1 + x = 3.605551275 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = 3.605551275 + -1 Combine like terms: 1 + -1 = 0 0 + x = 3.605551275 + -1 x = 3.605551275 + -1 Combine like terms: 3.605551275 + -1 = 2.605551275 x = 2.605551275 Simplifying x = 2.605551275

Subproblem 2

x + 1 = -3.605551275 Simplifying x + 1 = -3.605551275 Reorder the terms: 1 + x = -3.605551275 Solving 1 + x = -3.605551275 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = -3.605551275 + -1 Combine like terms: 1 + -1 = 0 0 + x = -3.605551275 + -1 x = -3.605551275 + -1 Combine like terms: -3.605551275 + -1 = -4.605551275 x = -4.605551275 Simplifying x = -4.605551275

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.605551275, -4.605551275}

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