w^2-4w=-21

Solution for w^2-4w=-21 equation:

Simplifying
w2 + -4w = -21

Reorder the terms:
-4w + w2 = -21

Solving
-4w + w2 = -21

Solving for variable 'w'.

Reorder the terms:
21 + -4w + w2 = -21 + 21

Combine like terms: -21 + 21 = 0
21 + -4w + w2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + -4w + -21 + w2 = 0 + -21

Reorder the terms:
21 + -21 + -4w + w2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -4w + w2 = 0 + -21
-4w + w2 = 0 + -21

Combine like terms: 0 + -21 = -21
-4w + w2 = -21

The w term is -4w.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4w + 4 + w2 = -21 + 4

Reorder the terms:
4 + -4w + w2 = -21 + 4

Combine like terms: -21 + 4 = -17
4 + -4w + w2 = -17

Factor a perfect square on the left side:
(w + -2)(w + -2) = -17

Can't calculate square root of the right side.

The solution to this equation could not be determined.