5x^2-10x-81=0

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Solution for 5x^2-10x-81=0 equation:


Simplifying
5x2 + -10x + -81 = 0

Reorder the terms:
-81 + -10x + 5x2 = 0

Solving
-81 + -10x + 5x2 = 0

Solving for variable 'x'.

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

Divide each side by '5'.
-16.2 + -2x + x2 = 0

Move the constant term to the right:

Add '16.2' to each side of the equation.
-16.2 + -2x + 16.2 + x2 = 0 + 16.2

Reorder the terms:
-16.2 + 16.2 + -2x + x2 = 0 + 16.2

Combine like terms: -16.2 + 16.2 = 0.0
0.0 + -2x + x2 = 0 + 16.2
-2x + x2 = 0 + 16.2

Combine like terms: 0 + 16.2 = 16.2
-2x + x2 = 16.2

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 = 16.2 + 1

Reorder the terms:
1 + -2x + x2 = 16.2 + 1

Combine like terms: 16.2 + 1 = 17.2
1 + -2x + x2 = 17.2

Factor a perfect square on the left side:
(x + -1)(x + -1) = 17.2

Calculate the square root of the right side: 4.147288271

Break this problem into two subproblems by setting 
(x + -1) equal to 4.147288271 and -4.147288271.

Subproblem 1

x + -1 = 4.147288271 Simplifying x + -1 = 4.147288271 Reorder the terms: -1 + x = 4.147288271 Solving -1 + x = 4.147288271 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 = 4.147288271 + 1 Combine like terms: -1 + 1 = 0 0 + x = 4.147288271 + 1 x = 4.147288271 + 1 Combine like terms: 4.147288271 + 1 = 5.147288271 x = 5.147288271 Simplifying x = 5.147288271

Subproblem 2

x + -1 = -4.147288271 Simplifying x + -1 = -4.147288271 Reorder the terms: -1 + x = -4.147288271 Solving -1 + x = -4.147288271 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 = -4.147288271 + 1 Combine like terms: -1 + 1 = 0 0 + x = -4.147288271 + 1 x = -4.147288271 + 1 Combine like terms: -4.147288271 + 1 = -3.147288271 x = -3.147288271 Simplifying x = -3.147288271

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.147288271, -3.147288271}

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