0=12+r-r^2

Solution for 0=12+r-r^2 equation:

Simplifying
0 = 12 + r + -1r2

Solving
0 = 12 + r + -1r2

Solving for variable 'r'.

Combine like terms: 0 + -12 = -12
-12 + -1r + r2 = 12 + r + -1r2 + -12 + -1r + r2

Reorder the terms:
-12 + -1r + r2 = 12 + -12 + r + -1r + -1r2 + r2

Combine like terms: 12 + -12 = 0
-12 + -1r + r2 = 0 + r + -1r + -1r2 + r2
-12 + -1r + r2 = r + -1r + -1r2 + r2

Combine like terms: r + -1r = 0
-12 + -1r + r2 = 0 + -1r2 + r2
-12 + -1r + r2 = -1r2 + r2

Combine like terms: -1r2 + r2 = 0
-12 + -1r + r2 = 0

Factor a trinomial.
(-3 + -1r)(4 + -1r) = 0

Subproblem 1
Set the factor '(-3 + -1r)' equal to zero and attempt to solve:

Simplifying
-3 + -1r = 0

Solving
-3 + -1r = 0

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

Add '3' to each side of the equation.
-3 + 3 + -1r = 0 + 3

Combine like terms: -3 + 3 = 0
0 + -1r = 0 + 3
-1r = 0 + 3

Combine like terms: 0 + 3 = 3
-1r = 3

Divide each side by '-1'.
r = -3

Simplifying
r = -3
Subproblem 2
Set the factor '(4 + -1r)' equal to zero and attempt to solve:

Simplifying
4 + -1r = 0

Solving
4 + -1r = 0

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

Add '-4' to each side of the equation.
4 + -4 + -1r = 0 + -4

Combine like terms: 4 + -4 = 0
0 + -1r = 0 + -4
-1r = 0 + -4

Combine like terms: 0 + -4 = -4
-1r = -4

Divide each side by '-1'.
r = 4

Simplifying
r = 4
Solution
r = {-3, 4}