u^2-22u+21=0

Solution for u^2-22u+21=0 equation:

Simplifying
u2 + -22u + 21 = 0

Reorder the terms:
21 + -22u + u2 = 0

Solving
21 + -22u + u2 = 0

Solving for variable 'u'.

Factor a trinomial.
(1 + -1u)(21 + -1u) = 0

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

Simplifying
1 + -1u = 0

Solving
1 + -1u = 0

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

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

Combine like terms: 1 + -1 = 0
0 + -1u = 0 + -1
-1u = 0 + -1

Combine like terms: 0 + -1 = -1
-1u = -1

Divide each side by '-1'.
u = 1

Simplifying
u = 1
Subproblem 2
Set the factor '(21 + -1u)' equal to zero and attempt to solve:

Simplifying
21 + -1u = 0

Solving
21 + -1u = 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 + -1u = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -1u = 0 + -21
-1u = 0 + -21

Combine like terms: 0 + -21 = -21
-1u = -21

Divide each side by '-1'.
u = 21

Simplifying
u = 21
Solution
u = {1, 21}