x^2-9x=-21

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Solution for x^2-9x=-21 equation:


Simplifying
x2 + -9x = -21

Reorder the terms:
-9x + x2 = -21

Solving
-9x + x2 = -21

Solving for variable 'x'.

Reorder the terms:
21 + -9x + x2 = -21 + 21

Combine like terms: -21 + 21 = 0
21 + -9x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + -9x + -21 + x2 = 0 + -21

Reorder the terms:
21 + -21 + -9x + x2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -9x + x2 = 0 + -21
-9x + x2 = 0 + -21

Combine like terms: 0 + -21 = -21
-9x + x2 = -21

The x term is -9x.  Take half its coefficient (-4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
-9x + 20.25 + x2 = -21 + 20.25

Reorder the terms:
20.25 + -9x + x2 = -21 + 20.25

Combine like terms: -21 + 20.25 = -0.75
20.25 + -9x + x2 = -0.75

Factor a perfect square on the left side:
(x + -4.5)(x + -4.5) = -0.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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