x^2+4x=84

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Solution for x^2+4x=84 equation:


Simplifying
x2 + 4x = 84

Reorder the terms:
4x + x2 = 84

Solving
4x + x2 = 84

Solving for variable 'x'.

Reorder the terms:
-84 + 4x + x2 = 84 + -84

Combine like terms: 84 + -84 = 0
-84 + 4x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '84' to each side of the equation.
-84 + 4x + 84 + x2 = 0 + 84

Reorder the terms:
-84 + 84 + 4x + x2 = 0 + 84

Combine like terms: -84 + 84 = 0
0 + 4x + x2 = 0 + 84
4x + x2 = 0 + 84

Combine like terms: 0 + 84 = 84
4x + x2 = 84

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 = 84 + 4

Reorder the terms:
4 + 4x + x2 = 84 + 4

Combine like terms: 84 + 4 = 88
4 + 4x + x2 = 88

Factor a perfect square on the left side:
(x + 2)(x + 2) = 88

Calculate the square root of the right side: 9.38083152

Break this problem into two subproblems by setting 
(x + 2) equal to 9.38083152 and -9.38083152.

Subproblem 1

x + 2 = 9.38083152 Simplifying x + 2 = 9.38083152 Reorder the terms: 2 + x = 9.38083152 Solving 2 + x = 9.38083152 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 = 9.38083152 + -2 Combine like terms: 2 + -2 = 0 0 + x = 9.38083152 + -2 x = 9.38083152 + -2 Combine like terms: 9.38083152 + -2 = 7.38083152 x = 7.38083152 Simplifying x = 7.38083152

Subproblem 2

x + 2 = -9.38083152 Simplifying x + 2 = -9.38083152 Reorder the terms: 2 + x = -9.38083152 Solving 2 + x = -9.38083152 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 = -9.38083152 + -2 Combine like terms: 2 + -2 = 0 0 + x = -9.38083152 + -2 x = -9.38083152 + -2 Combine like terms: -9.38083152 + -2 = -11.38083152 x = -11.38083152 Simplifying x = -11.38083152

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.38083152, -11.38083152}

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