u^2+21u=0

Solution for u^2+21u=0 equation:

Simplifying
u2 + 21u = 0

Reorder the terms:
21u + u2 = 0

Solving
21u + u2 = 0

Solving for variable 'u'.

Factor out the Greatest Common Factor (GCF), 'u'.
u(21 + u) = 0

Subproblem 1
Set the factor 'u' equal to zero and attempt to solve:

Simplifying
u = 0

Solving
u = 0

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

Simplifying
u = 0
Subproblem 2
Set the factor '(21 + u)' equal to zero and attempt to solve:

Simplifying
21 + u = 0

Solving
21 + u = 0

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

Add '-21' to each side of the equation.
21 + -21 + u = 0 + -21

Combine like terms: 21 + -21 = 0
0 + u = 0 + -21
u = 0 + -21

Combine like terms: 0 + -21 = -21
u = -21

Simplifying
u = -21
Solution
u = {0, -21}