a^2-21a+20=

Solution for a^2-21a+20= equation:

Simplifying
a2 + -21a + 20 = 0

Reorder the terms:
20 + -21a + a2 = 0

Solving
20 + -21a + a2 = 0

Solving for variable 'a'.

Factor a trinomial.
(1 + -1a)(20 + -1a) = 0

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

Simplifying
1 + -1a = 0

Solving
1 + -1a = 0

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

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

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

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

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

Simplifying
a = 1
Subproblem 2
Set the factor '(20 + -1a)' equal to zero and attempt to solve:

Simplifying
20 + -1a = 0

Solving
20 + -1a = 0

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

Add '-20' to each side of the equation.
20 + -20 + -1a = 0 + -20

Combine like terms: 20 + -20 = 0
0 + -1a = 0 + -20
-1a = 0 + -20

Combine like terms: 0 + -20 = -20
-1a = -20

Divide each side by '-1'.
a = 20

Simplifying
a = 20
Solution
a = {1, 20}