2x^2+x-21=8x^2

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Solution for 2x^2+x-21=8x^2 equation:


Simplifying
2x2 + x + -21 = 8x2

Reorder the terms:
-21 + x + 2x2 = 8x2

Solving
-21 + x + 2x2 = 8x2

Solving for variable 'x'.

Combine like terms: 2x2 + -8x2 = -6x2
-21 + x + -6x2 = 8x2 + -8x2

Combine like terms: 8x2 + -8x2 = 0
-21 + x + -6x2 = 0

Begin completing the square.  Divide all terms by
-6 the coefficient of the squared term: 

Divide each side by '-6'.
3.5 + -0.1666666667x + x2 = 0

Move the constant term to the right:

Add '-3.5' to each side of the equation.
3.5 + -0.1666666667x + -3.5 + x2 = 0 + -3.5

Reorder the terms:
3.5 + -3.5 + -0.1666666667x + x2 = 0 + -3.5

Combine like terms: 3.5 + -3.5 = 0.0
0.0 + -0.1666666667x + x2 = 0 + -3.5
-0.1666666667x + x2 = 0 + -3.5

Combine like terms: 0 + -3.5 = -3.5
-0.1666666667x + x2 = -3.5

The x term is x.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-0.1666666667x + 0.25 + x2 = -3.5 + 0.25

Reorder the terms:
0.25 + -0.1666666667x + x2 = -3.5 + 0.25

Combine like terms: -3.5 + 0.25 = -3.25
0.25 + -0.1666666667x + x2 = -3.25

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = -3.25

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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