5x^2+10x+21=0

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Solution for 5x^2+10x+21=0 equation:


Simplifying
5x2 + 10x + 21 = 0

Reorder the terms:
21 + 10x + 5x2 = 0

Solving
21 + 10x + 5x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
5 the coefficient of the squared term: 

Divide each side by '5'.
4.2 + 2x + x2 = 0

Move the constant term to the right:

Add '-4.2' to each side of the equation.
4.2 + 2x + -4.2 + x2 = 0 + -4.2

Reorder the terms:
4.2 + -4.2 + 2x + x2 = 0 + -4.2

Combine like terms: 4.2 + -4.2 = 0.0
0.0 + 2x + x2 = 0 + -4.2
2x + x2 = 0 + -4.2

Combine like terms: 0 + -4.2 = -4.2
2x + x2 = -4.2

The x term is 2x.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2x + 1 + x2 = -4.2 + 1

Reorder the terms:
1 + 2x + x2 = -4.2 + 1

Combine like terms: -4.2 + 1 = -3.2
1 + 2x + x2 = -3.2

Factor a perfect square on the left side:
(x + 1)(x + 1) = -3.2

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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