(r+11)(r-9)=

Solution for (r+11)(r-9)= equation:

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

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

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

Multiply (11 + r) * (-9 + r)
(11(-9 + r) + r(-9 + r)) = 0
((-9 * 11 + r * 11) + r(-9 + r)) = 0
((-99 + 11r) + r(-9 + r)) = 0
(-99 + 11r + (-9 * r + r * r)) = 0
(-99 + 11r + (-9r + r2)) = 0

Combine like terms: 11r + -9r = 2r
(-99 + 2r + r2) = 0

Solving
-99 + 2r + r2 = 0

Solving for variable 'r'.

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

Subproblem 1
Set the factor '(-11 + -1r)' equal to zero and attempt to solve:

Simplifying
-11 + -1r = 0

Solving
-11 + -1r = 0

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

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

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

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

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

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

Simplifying
9 + -1r = 0

Solving
9 + -1r = 0

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

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

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

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

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

Simplifying
r = 9
Solution
r = {-11, 9}