x^2-4x=42

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Solution for x^2-4x=42 equation:


Simplifying
x2 + -4x = 42

Reorder the terms:
-4x + x2 = 42

Solving
-4x + x2 = 42

Solving for variable 'x'.

Reorder the terms:
-42 + -4x + x2 = 42 + -42

Combine like terms: 42 + -42 = 0
-42 + -4x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '42' to each side of the equation.
-42 + -4x + 42 + x2 = 0 + 42

Reorder the terms:
-42 + 42 + -4x + x2 = 0 + 42

Combine like terms: -42 + 42 = 0
0 + -4x + x2 = 0 + 42
-4x + x2 = 0 + 42

Combine like terms: 0 + 42 = 42
-4x + x2 = 42

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 = 42 + 4

Reorder the terms:
4 + -4x + x2 = 42 + 4

Combine like terms: 42 + 4 = 46
4 + -4x + x2 = 46

Factor a perfect square on the left side:
(x + -2)(x + -2) = 46

Calculate the square root of the right side: 6.782329983

Break this problem into two subproblems by setting 
(x + -2) equal to 6.782329983 and -6.782329983.

Subproblem 1

x + -2 = 6.782329983 Simplifying x + -2 = 6.782329983 Reorder the terms: -2 + x = 6.782329983 Solving -2 + x = 6.782329983 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 = 6.782329983 + 2 Combine like terms: -2 + 2 = 0 0 + x = 6.782329983 + 2 x = 6.782329983 + 2 Combine like terms: 6.782329983 + 2 = 8.782329983 x = 8.782329983 Simplifying x = 8.782329983

Subproblem 2

x + -2 = -6.782329983 Simplifying x + -2 = -6.782329983 Reorder the terms: -2 + x = -6.782329983 Solving -2 + x = -6.782329983 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 = -6.782329983 + 2 Combine like terms: -2 + 2 = 0 0 + x = -6.782329983 + 2 x = -6.782329983 + 2 Combine like terms: -6.782329983 + 2 = -4.782329983 x = -4.782329983 Simplifying x = -4.782329983

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.782329983, -4.782329983}

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