k^2=-21+10k

Solution for k^2=-21+10k equation:

Simplifying
k2 = -21 + 10k

Solving
k2 = -21 + 10k

Solving for variable 'k'.

Reorder the terms:
21 + -10k + k2 = -21 + 10k + 21 + -10k

Reorder the terms:
21 + -10k + k2 = -21 + 21 + 10k + -10k

Combine like terms: -21 + 21 = 0
21 + -10k + k2 = 0 + 10k + -10k
21 + -10k + k2 = 10k + -10k

Combine like terms: 10k + -10k = 0
21 + -10k + k2 = 0

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

Subproblem 1
Set the factor '(3 + -1k)' equal to zero and attempt to solve:

Simplifying
3 + -1k = 0

Solving
3 + -1k = 0

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

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

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

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

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

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

Simplifying
7 + -1k = 0

Solving
7 + -1k = 0

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

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

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

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

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

Simplifying
k = 7
Solution
k = {3, 7}