p^2-20p-21=0

Solution for p^2-20p-21=0 equation:

Simplifying
p2 + -20p + -21 = 0

Reorder the terms:
-21 + -20p + p2 = 0

Solving
-21 + -20p + p2 = 0

Solving for variable 'p'.

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

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

Simplifying
-1 + -1p = 0

Solving
-1 + -1p = 0

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

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

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

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

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

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

Simplifying
21 + -1p = 0

Solving
21 + -1p = 0

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

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

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

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

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

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