2*x^2+82*x+81=0

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Solution for 2*x^2+82*x+81=0 equation:


Simplifying
2x2 + 82x + 81 = 0

Reorder the terms:
81 + 82x + 2x2 = 0

Solving
81 + 82x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
40.5 + 41x + x2 = 0

Move the constant term to the right:

Add '-40.5' to each side of the equation.
40.5 + 41x + -40.5 + x2 = 0 + -40.5

Reorder the terms:
40.5 + -40.5 + 41x + x2 = 0 + -40.5

Combine like terms: 40.5 + -40.5 = 0.0
0.0 + 41x + x2 = 0 + -40.5
41x + x2 = 0 + -40.5

Combine like terms: 0 + -40.5 = -40.5
41x + x2 = -40.5

The x term is 41x.  Take half its coefficient (20.5).
Square it (420.25) and add it to both sides.

Add '420.25' to each side of the equation.
41x + 420.25 + x2 = -40.5 + 420.25

Reorder the terms:
420.25 + 41x + x2 = -40.5 + 420.25

Combine like terms: -40.5 + 420.25 = 379.75
420.25 + 41x + x2 = 379.75

Factor a perfect square on the left side:
(x + 20.5)(x + 20.5) = 379.75

Calculate the square root of the right side: 19.48717527

Break this problem into two subproblems by setting 
(x + 20.5) equal to 19.48717527 and -19.48717527.

Subproblem 1

x + 20.5 = 19.48717527 Simplifying x + 20.5 = 19.48717527 Reorder the terms: 20.5 + x = 19.48717527 Solving 20.5 + x = 19.48717527 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-20.5' to each side of the equation. 20.5 + -20.5 + x = 19.48717527 + -20.5 Combine like terms: 20.5 + -20.5 = 0.0 0.0 + x = 19.48717527 + -20.5 x = 19.48717527 + -20.5 Combine like terms: 19.48717527 + -20.5 = -1.01282473 x = -1.01282473 Simplifying x = -1.01282473

Subproblem 2

x + 20.5 = -19.48717527 Simplifying x + 20.5 = -19.48717527 Reorder the terms: 20.5 + x = -19.48717527 Solving 20.5 + x = -19.48717527 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-20.5' to each side of the equation. 20.5 + -20.5 + x = -19.48717527 + -20.5 Combine like terms: 20.5 + -20.5 = 0.0 0.0 + x = -19.48717527 + -20.5 x = -19.48717527 + -20.5 Combine like terms: -19.48717527 + -20.5 = -39.98717527 x = -39.98717527 Simplifying x = -39.98717527

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-1.01282473, -39.98717527}

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