s^2+8s+21=0

Solution for s^2+8s+21=0 equation:

Simplifying
s2 + 8s + 21 = 0

Reorder the terms:
21 + 8s + s2 = 0

Solving
21 + 8s + s2 = 0

Solving for variable 's'.

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + 8s + -21 + s2 = 0 + -21

Reorder the terms:
21 + -21 + 8s + s2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + 8s + s2 = 0 + -21
8s + s2 = 0 + -21

Combine like terms: 0 + -21 = -21
8s + s2 = -21

The s term is 8s.  Take half its coefficient (4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
8s + 16 + s2 = -21 + 16

Reorder the terms:
16 + 8s + s2 = -21 + 16

Combine like terms: -21 + 16 = -5
16 + 8s + s2 = -5

Factor a perfect square on the left side:
(s + 4)(s + 4) = -5

Can't calculate square root of the right side.

The solution to this equation could not be determined.