(y-9)(y-11)=0

Solution for (y-9)(y-11)=0 equation:

Simplifying
(y + -9)(y + -11) = 0

Reorder the terms:
(-9 + y)(y + -11) = 0

Reorder the terms:
(-9 + y)(-11 + y) = 0

Multiply (-9 + y) * (-11 + y)
(-9(-11 + y) + y(-11 + y)) = 0
((-11 * -9 + y * -9) + y(-11 + y)) = 0
((99 + -9y) + y(-11 + y)) = 0
(99 + -9y + (-11 * y + y * y)) = 0
(99 + -9y + (-11y + y2)) = 0

Combine like terms: -9y + -11y = -20y
(99 + -20y + y2) = 0

Solving
99 + -20y + y2 = 0

Solving for variable 'y'.

Factor a trinomial.
(9 + -1y)(11 + -1y) = 0

Subproblem 1
Set the factor '(9 + -1y)' equal to zero and attempt to solve:

Simplifying
9 + -1y = 0

Solving
9 + -1y = 0

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

Add '-9' to each side of the equation.
9 + -9 + -1y = 0 + -9

Combine like terms: 9 + -9 = 0
0 + -1y = 0 + -9
-1y = 0 + -9

Combine like terms: 0 + -9 = -9
-1y = -9

Divide each side by '-1'.
y = 9

Simplifying
y = 9
Subproblem 2
Set the factor '(11 + -1y)' equal to zero and attempt to solve:

Simplifying
11 + -1y = 0

Solving
11 + -1y = 0

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

Add '-11' to each side of the equation.
11 + -11 + -1y = 0 + -11

Combine like terms: 11 + -11 = 0
0 + -1y = 0 + -11
-1y = 0 + -11

Combine like terms: 0 + -11 = -11
-1y = -11

Divide each side by '-1'.
y = 11

Simplifying
y = 11
Solution
y = {9, 11}