x^2+20x=-90

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Solution for x^2+20x=-90 equation:


Simplifying
x2 + 20x = -90

Reorder the terms:
20x + x2 = -90

Solving
20x + x2 = -90

Solving for variable 'x'.

Reorder the terms:
90 + 20x + x2 = -90 + 90

Combine like terms: -90 + 90 = 0
90 + 20x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-90' to each side of the equation.
90 + 20x + -90 + x2 = 0 + -90

Reorder the terms:
90 + -90 + 20x + x2 = 0 + -90

Combine like terms: 90 + -90 = 0
0 + 20x + x2 = 0 + -90
20x + x2 = 0 + -90

Combine like terms: 0 + -90 = -90
20x + x2 = -90

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 = -90 + 100

Reorder the terms:
100 + 20x + x2 = -90 + 100

Combine like terms: -90 + 100 = 10
100 + 20x + x2 = 10

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

Calculate the square root of the right side: 3.16227766

Break this problem into two subproblems by setting 
(x + 10) equal to 3.16227766 and -3.16227766.

Subproblem 1

x + 10 = 3.16227766 Simplifying x + 10 = 3.16227766 Reorder the terms: 10 + x = 3.16227766 Solving 10 + x = 3.16227766 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 = 3.16227766 + -10 Combine like terms: 10 + -10 = 0 0 + x = 3.16227766 + -10 x = 3.16227766 + -10 Combine like terms: 3.16227766 + -10 = -6.83772234 x = -6.83772234 Simplifying x = -6.83772234

Subproblem 2

x + 10 = -3.16227766 Simplifying x + 10 = -3.16227766 Reorder the terms: 10 + x = -3.16227766 Solving 10 + x = -3.16227766 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 = -3.16227766 + -10 Combine like terms: 10 + -10 = 0 0 + x = -3.16227766 + -10 x = -3.16227766 + -10 Combine like terms: -3.16227766 + -10 = -13.16227766 x = -13.16227766 Simplifying x = -13.16227766

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-6.83772234, -13.16227766}

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