4=x^2-8x

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Solution for 4=x^2-8x equation:


Simplifying
4 = x2 + -8x

Reorder the terms:
4 = -8x + x2

Solving
4 = -8x + x2

Solving for variable 'x'.

Reorder the terms:
4 + 8x + -1x2 = -8x + 8x + x2 + -1x2

Combine like terms: -8x + 8x = 0
4 + 8x + -1x2 = 0 + x2 + -1x2
4 + 8x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
4 + 8x + -1x2 = 0

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

Divide each side by '-1'.
-4 + -8x + x2 = 0

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + -8x + 4 + x2 = 0 + 4

Reorder the terms:
-4 + 4 + -8x + x2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -8x + x2 = 0 + 4
-8x + x2 = 0 + 4

Combine like terms: 0 + 4 = 4
-8x + x2 = 4

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 = 4 + 16

Reorder the terms:
16 + -8x + x2 = 4 + 16

Combine like terms: 4 + 16 = 20
16 + -8x + x2 = 20

Factor a perfect square on the left side:
(x + -4)(x + -4) = 20

Calculate the square root of the right side: 4.472135955

Break this problem into two subproblems by setting 
(x + -4) equal to 4.472135955 and -4.472135955.

Subproblem 1

x + -4 = 4.472135955 Simplifying x + -4 = 4.472135955 Reorder the terms: -4 + x = 4.472135955 Solving -4 + x = 4.472135955 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 = 4.472135955 + 4 Combine like terms: -4 + 4 = 0 0 + x = 4.472135955 + 4 x = 4.472135955 + 4 Combine like terms: 4.472135955 + 4 = 8.472135955 x = 8.472135955 Simplifying x = 8.472135955

Subproblem 2

x + -4 = -4.472135955 Simplifying x + -4 = -4.472135955 Reorder the terms: -4 + x = -4.472135955 Solving -4 + x = -4.472135955 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 = -4.472135955 + 4 Combine like terms: -4 + 4 = 0 0 + x = -4.472135955 + 4 x = -4.472135955 + 4 Combine like terms: -4.472135955 + 4 = -0.472135955 x = -0.472135955 Simplifying x = -0.472135955

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.472135955, -0.472135955}

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