x^2-2x-84=0

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


Simplifying
x2 + -2x + -84 = 0

Reorder the terms:
-84 + -2x + x2 = 0

Solving
-84 + -2x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '84' to each side of the equation.
-84 + -2x + 84 + x2 = 0 + 84

Reorder the terms:
-84 + 84 + -2x + x2 = 0 + 84

Combine like terms: -84 + 84 = 0
0 + -2x + x2 = 0 + 84
-2x + x2 = 0 + 84

Combine like terms: 0 + 84 = 84
-2x + x2 = 84

The x term is -2x.  Take half its coefficient (-1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
-2x + 1 + x2 = 84 + 1

Reorder the terms:
1 + -2x + x2 = 84 + 1

Combine like terms: 84 + 1 = 85
1 + -2x + x2 = 85

Factor a perfect square on the left side:
(x + -1)(x + -1) = 85

Calculate the square root of the right side: 9.219544457

Break this problem into two subproblems by setting 
(x + -1) equal to 9.219544457 and -9.219544457.

Subproblem 1

x + -1 = 9.219544457 Simplifying x + -1 = 9.219544457 Reorder the terms: -1 + x = 9.219544457 Solving -1 + x = 9.219544457 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + x = 9.219544457 + 1 Combine like terms: -1 + 1 = 0 0 + x = 9.219544457 + 1 x = 9.219544457 + 1 Combine like terms: 9.219544457 + 1 = 10.219544457 x = 10.219544457 Simplifying x = 10.219544457

Subproblem 2

x + -1 = -9.219544457 Simplifying x + -1 = -9.219544457 Reorder the terms: -1 + x = -9.219544457 Solving -1 + x = -9.219544457 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + x = -9.219544457 + 1 Combine like terms: -1 + 1 = 0 0 + x = -9.219544457 + 1 x = -9.219544457 + 1 Combine like terms: -9.219544457 + 1 = -8.219544457 x = -8.219544457 Simplifying x = -8.219544457

Solution

The solution to the problem is based on the solutions from the subproblems. x = {10.219544457, -8.219544457}

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