x^2+21x+10=0

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Solution for x^2+21x+10=0 equation:


Simplifying
x2 + 21x + 10 = 0

Reorder the terms:
10 + 21x + x2 = 0

Solving
10 + 21x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '-10' to each side of the equation.
10 + 21x + -10 + x2 = 0 + -10

Reorder the terms:
10 + -10 + 21x + x2 = 0 + -10

Combine like terms: 10 + -10 = 0
0 + 21x + x2 = 0 + -10
21x + x2 = 0 + -10

Combine like terms: 0 + -10 = -10
21x + x2 = -10

The x term is 21x.  Take half its coefficient (10.5).
Square it (110.25) and add it to both sides.

Add '110.25' to each side of the equation.
21x + 110.25 + x2 = -10 + 110.25

Reorder the terms:
110.25 + 21x + x2 = -10 + 110.25

Combine like terms: -10 + 110.25 = 100.25
110.25 + 21x + x2 = 100.25

Factor a perfect square on the left side:
(x + 10.5)(x + 10.5) = 100.25

Calculate the square root of the right side: 10.012492197

Break this problem into two subproblems by setting 
(x + 10.5) equal to 10.012492197 and -10.012492197.

Subproblem 1

x + 10.5 = 10.012492197 Simplifying x + 10.5 = 10.012492197 Reorder the terms: 10.5 + x = 10.012492197 Solving 10.5 + x = 10.012492197 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-10.5' to each side of the equation. 10.5 + -10.5 + x = 10.012492197 + -10.5 Combine like terms: 10.5 + -10.5 = 0.0 0.0 + x = 10.012492197 + -10.5 x = 10.012492197 + -10.5 Combine like terms: 10.012492197 + -10.5 = -0.487507803 x = -0.487507803 Simplifying x = -0.487507803

Subproblem 2

x + 10.5 = -10.012492197 Simplifying x + 10.5 = -10.012492197 Reorder the terms: 10.5 + x = -10.012492197 Solving 10.5 + x = -10.012492197 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-10.5' to each side of the equation. 10.5 + -10.5 + x = -10.012492197 + -10.5 Combine like terms: 10.5 + -10.5 = 0.0 0.0 + x = -10.012492197 + -10.5 x = -10.012492197 + -10.5 Combine like terms: -10.012492197 + -10.5 = -20.512492197 x = -20.512492197 Simplifying x = -20.512492197

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-0.487507803, -20.512492197}

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