-x^2+2x-21=0

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


Simplifying
-1x2 + 2x + -21 = 0

Reorder the terms:
-21 + 2x + -1x2 = 0

Solving
-21 + 2x + -1x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
21 + -2x + x2 = 0

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + -2x + -21 + x2 = 0 + -21

Reorder the terms:
21 + -21 + -2x + x2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -2x + x2 = 0 + -21
-2x + x2 = 0 + -21

Combine like terms: 0 + -21 = -21
-2x + x2 = -21

The x term is -2x.  Take half its coefficient (-1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
-2x + 1 + x2 = -21 + 1

Reorder the terms:
1 + -2x + x2 = -21 + 1

Combine like terms: -21 + 1 = -20
1 + -2x + x2 = -20

Factor a perfect square on the left side:
(x + -1)(x + -1) = -20

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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