4x^2+5x+21=0

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Solution for 4x^2+5x+21=0 equation:


Simplifying
4x2 + 5x + 21 = 0

Reorder the terms:
21 + 5x + 4x2 = 0

Solving
21 + 5x + 4x2 = 0

Solving for variable 'x'.

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

Divide each side by '4'.
5.25 + 1.25x + x2 = 0

Move the constant term to the right:

Add '-5.25' to each side of the equation.
5.25 + 1.25x + -5.25 + x2 = 0 + -5.25

Reorder the terms:
5.25 + -5.25 + 1.25x + x2 = 0 + -5.25

Combine like terms: 5.25 + -5.25 = 0.00
0.00 + 1.25x + x2 = 0 + -5.25
1.25x + x2 = 0 + -5.25

Combine like terms: 0 + -5.25 = -5.25
1.25x + x2 = -5.25

The x term is 1.25x.  Take half its coefficient (0.625).
Square it (0.390625) and add it to both sides.

Add '0.390625' to each side of the equation.
1.25x + 0.390625 + x2 = -5.25 + 0.390625

Reorder the terms:
0.390625 + 1.25x + x2 = -5.25 + 0.390625

Combine like terms: -5.25 + 0.390625 = -4.859375
0.390625 + 1.25x + x2 = -4.859375

Factor a perfect square on the left side:
(x + 0.625)(x + 0.625) = -4.859375

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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