x^2+81=-20x

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Solution for x^2+81=-20x equation:


Simplifying
x2 + 81 = -20x

Reorder the terms:
81 + x2 = -20x

Solving
81 + x2 = -20x

Solving for variable 'x'.

Reorder the terms:
81 + 20x + x2 = -20x + 20x

Combine like terms: -20x + 20x = 0
81 + 20x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-81' to each side of the equation.
81 + 20x + -81 + x2 = 0 + -81

Reorder the terms:
81 + -81 + 20x + x2 = 0 + -81

Combine like terms: 81 + -81 = 0
0 + 20x + x2 = 0 + -81
20x + x2 = 0 + -81

Combine like terms: 0 + -81 = -81
20x + x2 = -81

The x term is 20x.  Take half its coefficient (10).
Square it (100) and add it to both sides.

Add '100' to each side of the equation.
20x + 100 + x2 = -81 + 100

Reorder the terms:
100 + 20x + x2 = -81 + 100

Combine like terms: -81 + 100 = 19
100 + 20x + x2 = 19

Factor a perfect square on the left side:
(x + 10)(x + 10) = 19

Calculate the square root of the right side: 4.358898944

Break this problem into two subproblems by setting 
(x + 10) equal to 4.358898944 and -4.358898944.

Subproblem 1

x + 10 = 4.358898944 Simplifying x + 10 = 4.358898944 Reorder the terms: 10 + x = 4.358898944 Solving 10 + x = 4.358898944 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-10' to each side of the equation. 10 + -10 + x = 4.358898944 + -10 Combine like terms: 10 + -10 = 0 0 + x = 4.358898944 + -10 x = 4.358898944 + -10 Combine like terms: 4.358898944 + -10 = -5.641101056 x = -5.641101056 Simplifying x = -5.641101056

Subproblem 2

x + 10 = -4.358898944 Simplifying x + 10 = -4.358898944 Reorder the terms: 10 + x = -4.358898944 Solving 10 + x = -4.358898944 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-10' to each side of the equation. 10 + -10 + x = -4.358898944 + -10 Combine like terms: 10 + -10 = 0 0 + x = -4.358898944 + -10 x = -4.358898944 + -10 Combine like terms: -4.358898944 + -10 = -14.358898944 x = -14.358898944 Simplifying x = -14.358898944

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-5.641101056, -14.358898944}

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