r^2+6r+21=

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Solution for r^2+6r+21= equation:


Simplifying
r2 + 6r + 21 = 0

Reorder the terms:
21 + 6r + r2 = 0

Solving
21 + 6r + r2 = 0

Solving for variable 'r'.

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + 6r + -21 + r2 = 0 + -21

Reorder the terms:
21 + -21 + 6r + r2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + 6r + r2 = 0 + -21
6r + r2 = 0 + -21

Combine like terms: 0 + -21 = -21
6r + r2 = -21

The r term is 6r.  Take half its coefficient (3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
6r + 9 + r2 = -21 + 9

Reorder the terms:
9 + 6r + r2 = -21 + 9

Combine like terms: -21 + 9 = -12
9 + 6r + r2 = -12

Factor a perfect square on the left side:
(r + 3)(r + 3) = -12

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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