x^2+20x+21=

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Solution for x^2+20x+21= equation:


Simplifying
x2 + 20x + 21 = 0

Reorder the terms:
21 + 20x + x2 = 0

Solving
21 + 20x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + 20x + -21 + x2 = 0 + -21

Reorder the terms:
21 + -21 + 20x + x2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + 20x + x2 = 0 + -21
20x + x2 = 0 + -21

Combine like terms: 0 + -21 = -21
20x + x2 = -21

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 = -21 + 100

Reorder the terms:
100 + 20x + x2 = -21 + 100

Combine like terms: -21 + 100 = 79
100 + 20x + x2 = 79

Factor a perfect square on the left side:
(x + 10)(x + 10) = 79

Calculate the square root of the right side: 8.888194417

Break this problem into two subproblems by setting 
(x + 10) equal to 8.888194417 and -8.888194417.

Subproblem 1

x + 10 = 8.888194417 Simplifying x + 10 = 8.888194417 Reorder the terms: 10 + x = 8.888194417 Solving 10 + x = 8.888194417 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 = 8.888194417 + -10 Combine like terms: 10 + -10 = 0 0 + x = 8.888194417 + -10 x = 8.888194417 + -10 Combine like terms: 8.888194417 + -10 = -1.111805583 x = -1.111805583 Simplifying x = -1.111805583

Subproblem 2

x + 10 = -8.888194417 Simplifying x + 10 = -8.888194417 Reorder the terms: 10 + x = -8.888194417 Solving 10 + x = -8.888194417 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 = -8.888194417 + -10 Combine like terms: 10 + -10 = 0 0 + x = -8.888194417 + -10 x = -8.888194417 + -10 Combine like terms: -8.888194417 + -10 = -18.888194417 x = -18.888194417 Simplifying x = -18.888194417

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-1.111805583, -18.888194417}

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