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}