2x^2+12x+21=0

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Solution for 2x^2+12x+21=0 equation:


Simplifying
2x2 + 12x + 21 = 0

Reorder the terms:
21 + 12x + 2x2 = 0

Solving
21 + 12x + 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'.
10.5 + 6x + x2 = 0

Move the constant term to the right:

Add '-10.5' to each side of the equation.
10.5 + 6x + -10.5 + x2 = 0 + -10.5

Reorder the terms:
10.5 + -10.5 + 6x + x2 = 0 + -10.5

Combine like terms: 10.5 + -10.5 = 0.0
0.0 + 6x + x2 = 0 + -10.5
6x + x2 = 0 + -10.5

Combine like terms: 0 + -10.5 = -10.5
6x + x2 = -10.5

The x term is 6x.  Take half its coefficient (3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
6x + 9 + x2 = -10.5 + 9

Reorder the terms:
9 + 6x + x2 = -10.5 + 9

Combine like terms: -10.5 + 9 = -1.5
9 + 6x + x2 = -1.5

Factor a perfect square on the left side:
(x + 3)(x + 3) = -1.5

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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