x^2+84x-18=0

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Solution for x^2+84x-18=0 equation:


Simplifying
x2 + 84x + -18 = 0

Reorder the terms:
-18 + 84x + x2 = 0

Solving
-18 + 84x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '18' to each side of the equation.
-18 + 84x + 18 + x2 = 0 + 18

Reorder the terms:
-18 + 18 + 84x + x2 = 0 + 18

Combine like terms: -18 + 18 = 0
0 + 84x + x2 = 0 + 18
84x + x2 = 0 + 18

Combine like terms: 0 + 18 = 18
84x + x2 = 18

The x term is 84x.  Take half its coefficient (42).
Square it (1764) and add it to both sides.

Add '1764' to each side of the equation.
84x + 1764 + x2 = 18 + 1764

Reorder the terms:
1764 + 84x + x2 = 18 + 1764

Combine like terms: 18 + 1764 = 1782
1764 + 84x + x2 = 1782

Factor a perfect square on the left side:
(x + 42)(x + 42) = 1782

Calculate the square root of the right side: 42.213741838

Break this problem into two subproblems by setting 
(x + 42) equal to 42.213741838 and -42.213741838.

Subproblem 1

x + 42 = 42.213741838 Simplifying x + 42 = 42.213741838 Reorder the terms: 42 + x = 42.213741838 Solving 42 + x = 42.213741838 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-42' to each side of the equation. 42 + -42 + x = 42.213741838 + -42 Combine like terms: 42 + -42 = 0 0 + x = 42.213741838 + -42 x = 42.213741838 + -42 Combine like terms: 42.213741838 + -42 = 0.213741838 x = 0.213741838 Simplifying x = 0.213741838

Subproblem 2

x + 42 = -42.213741838 Simplifying x + 42 = -42.213741838 Reorder the terms: 42 + x = -42.213741838 Solving 42 + x = -42.213741838 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-42' to each side of the equation. 42 + -42 + x = -42.213741838 + -42 Combine like terms: 42 + -42 = 0 0 + x = -42.213741838 + -42 x = -42.213741838 + -42 Combine like terms: -42.213741838 + -42 = -84.213741838 x = -84.213741838 Simplifying x = -84.213741838

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.213741838, -84.213741838}

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