-21x^2+8x-4=0

Solution for -21x^2+8x-4=0 equation:

Simplifying
-21x2 + 8x + -4 = 0

Reorder the terms:
-4 + 8x + -21x2 = 0

Solving
-4 + 8x + -21x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
-21 the coefficient of the squared term: 

Divide each side by '-21'.
0.1904761905 + -0.380952381x + x2 = 0

Move the constant term to the right:

Add '-0.1904761905' to each side of the equation.
0.1904761905 + -0.380952381x + -0.1904761905 + x2 = 0 + -0.1904761905

Reorder the terms:
0.1904761905 + -0.1904761905 + -0.380952381x + x2 = 0 + -0.1904761905

Combine like terms: 0.1904761905 + -0.1904761905 = 0.0000000000
0.0000000000 + -0.380952381x + x2 = 0 + -0.1904761905
-0.380952381x + x2 = 0 + -0.1904761905

Combine like terms: 0 + -0.1904761905 = -0.1904761905
-0.380952381x + x2 = -0.1904761905

The x term is -0.380952381x.  Take half its coefficient (-0.1904761905).
Square it (0.03628117915) and add it to both sides.

Add '0.03628117915' to each side of the equation.
-0.380952381x + 0.03628117915 + x2 = -0.1904761905 + 0.03628117915

Reorder the terms:
0.03628117915 + -0.380952381x + x2 = -0.1904761905 + 0.03628117915

Combine like terms: -0.1904761905 + 0.03628117915 = -0.15419501135
0.03628117915 + -0.380952381x + x2 = -0.15419501135

Factor a perfect square on the left side:
(x + -0.1904761905)(x + -0.1904761905) = -0.15419501135

Can't calculate square root of the right side.

The solution to this equation could not be determined.