x^2+8x=39

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Solution for x^2+8x=39 equation:


Simplifying
x2 + 8x = 39

Reorder the terms:
8x + x2 = 39

Solving
8x + x2 = 39

Solving for variable 'x'.

Reorder the terms:
-39 + 8x + x2 = 39 + -39

Combine like terms: 39 + -39 = 0
-39 + 8x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '39' to each side of the equation.
-39 + 8x + 39 + x2 = 0 + 39

Reorder the terms:
-39 + 39 + 8x + x2 = 0 + 39

Combine like terms: -39 + 39 = 0
0 + 8x + x2 = 0 + 39
8x + x2 = 0 + 39

Combine like terms: 0 + 39 = 39
8x + x2 = 39

The x term is 8x.  Take half its coefficient (4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
8x + 16 + x2 = 39 + 16

Reorder the terms:
16 + 8x + x2 = 39 + 16

Combine like terms: 39 + 16 = 55
16 + 8x + x2 = 55

Factor a perfect square on the left side:
(x + 4)(x + 4) = 55

Calculate the square root of the right side: 7.416198487

Break this problem into two subproblems by setting 
(x + 4) equal to 7.416198487 and -7.416198487.

Subproblem 1

x + 4 = 7.416198487 Simplifying x + 4 = 7.416198487 Reorder the terms: 4 + x = 7.416198487 Solving 4 + x = 7.416198487 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + x = 7.416198487 + -4 Combine like terms: 4 + -4 = 0 0 + x = 7.416198487 + -4 x = 7.416198487 + -4 Combine like terms: 7.416198487 + -4 = 3.416198487 x = 3.416198487 Simplifying x = 3.416198487

Subproblem 2

x + 4 = -7.416198487 Simplifying x + 4 = -7.416198487 Reorder the terms: 4 + x = -7.416198487 Solving 4 + x = -7.416198487 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + x = -7.416198487 + -4 Combine like terms: 4 + -4 = 0 0 + x = -7.416198487 + -4 x = -7.416198487 + -4 Combine like terms: -7.416198487 + -4 = -11.416198487 x = -11.416198487 Simplifying x = -11.416198487

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.416198487, -11.416198487}

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