a^2-a+21=0

Solution for a^2-a+21=0 equation:

Simplifying
a2 + -1a + 21 = 0

Reorder the terms:
21 + -1a + a2 = 0

Solving
21 + -1a + a2 = 0

Solving for variable 'a'.

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + -1a + -21 + a2 = 0 + -21

Reorder the terms:
21 + -21 + -1a + a2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -1a + a2 = 0 + -21
-1a + a2 = 0 + -21

Combine like terms: 0 + -21 = -21
-1a + a2 = -21

The a term is -1a.  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.
-1a + 0.25 + a2 = -21 + 0.25

Reorder the terms:
0.25 + -1a + a2 = -21 + 0.25

Combine like terms: -21 + 0.25 = -20.75
0.25 + -1a + a2 = -20.75

Factor a perfect square on the left side:
(a + -0.5)(a + -0.5) = -20.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.