k^2+20k-21=0

Solution for k^2+20k-21=0 equation:

Simplifying
k2 + 20k + -21 = 0

Reorder the terms:
-21 + 20k + k2 = 0

Solving
-21 + 20k + k2 = 0

Solving for variable 'k'.

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

Subproblem 1
Set the factor '(-21 + -1k)' equal to zero and attempt to solve:

Simplifying
-21 + -1k = 0

Solving
-21 + -1k = 0

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

Add '21' to each side of the equation.
-21 + 21 + -1k = 0 + 21

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

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

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

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

Simplifying
1 + -1k = 0

Solving
1 + -1k = 0

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

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

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

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

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

Simplifying
k = 1
Solution
k = {-21, 1}