3x^2+5x+21=0

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Solution for 3x^2+5x+21=0 equation:


Simplifying
3x2 + 5x + 21 = 0

Reorder the terms:
21 + 5x + 3x2 = 0

Solving
21 + 5x + 3x2 = 0

Solving for variable 'x'.

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

Divide each side by '3'.
7 + 1.666666667x + x2 = 0

Move the constant term to the right:

Add '-7' to each side of the equation.
7 + 1.666666667x + -7 + x2 = 0 + -7

Reorder the terms:
7 + -7 + 1.666666667x + x2 = 0 + -7

Combine like terms: 7 + -7 = 0
0 + 1.666666667x + x2 = 0 + -7
1.666666667x + x2 = 0 + -7

Combine like terms: 0 + -7 = -7
1.666666667x + x2 = -7

The x term is 1.666666667x.  Take half its coefficient (0.8333333335).
Square it (0.6944444447) and add it to both sides.

Add '0.6944444447' to each side of the equation.
1.666666667x + 0.6944444447 + x2 = -7 + 0.6944444447

Reorder the terms:
0.6944444447 + 1.666666667x + x2 = -7 + 0.6944444447

Combine like terms: -7 + 0.6944444447 = -6.3055555553
0.6944444447 + 1.666666667x + x2 = -6.3055555553

Factor a perfect square on the left side:
(x + 0.8333333335)(x + 0.8333333335) = -6.3055555553

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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