s^2+4s-21=0

Solution for s^2+4s-21=0 equation:

Simplifying
s2 + 4s + -21 = 0

Reorder the terms:
-21 + 4s + s2 = 0

Solving
-21 + 4s + s2 = 0

Solving for variable 's'.

Factor a trinomial.
(-7 + -1s)(3 + -1s) = 0

Subproblem 1
Set the factor '(-7 + -1s)' equal to zero and attempt to solve:

Simplifying
-7 + -1s = 0

Solving
-7 + -1s = 0

Move all terms containing s to the left, all other terms to the right.

Add '7' to each side of the equation.
-7 + 7 + -1s = 0 + 7

Combine like terms: -7 + 7 = 0
0 + -1s = 0 + 7
-1s = 0 + 7

Combine like terms: 0 + 7 = 7
-1s = 7

Divide each side by '-1'.
s = -7

Simplifying
s = -7
Subproblem 2
Set the factor '(3 + -1s)' equal to zero and attempt to solve:

Simplifying
3 + -1s = 0

Solving
3 + -1s = 0

Move all terms containing s to the left, all other terms to the right.

Add '-3' to each side of the equation.
3 + -3 + -1s = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -1s = 0 + -3
-1s = 0 + -3

Combine like terms: 0 + -3 = -3
-1s = -3

Divide each side by '-1'.
s = 3

Simplifying
s = 3
Solution
s = {-7, 3}