0=12-r^2+4r

Solution for 0=12-r^2+4r equation:

Simplifying
0 = 12 + -1r2 + 4r

Reorder the terms:
0 = 12 + 4r + -1r2

Solving
0 = 12 + 4r + -1r2

Solving for variable 'r'.

Combine like terms: 0 + -12 = -12
-12 + -4r + r2 = 12 + 4r + -1r2 + -12 + -4r + r2

Reorder the terms:
-12 + -4r + r2 = 12 + -12 + 4r + -4r + -1r2 + r2

Combine like terms: 12 + -12 = 0
-12 + -4r + r2 = 0 + 4r + -4r + -1r2 + r2
-12 + -4r + r2 = 4r + -4r + -1r2 + r2

Combine like terms: 4r + -4r = 0
-12 + -4r + r2 = 0 + -1r2 + r2
-12 + -4r + r2 = -1r2 + r2

Combine like terms: -1r2 + r2 = 0
-12 + -4r + r2 = 0

Factor a trinomial.
(-2 + -1r)(6 + -1r) = 0

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

Simplifying
-2 + -1r = 0

Solving
-2 + -1r = 0

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

Add '2' to each side of the equation.
-2 + 2 + -1r = 0 + 2

Combine like terms: -2 + 2 = 0
0 + -1r = 0 + 2
-1r = 0 + 2

Combine like terms: 0 + 2 = 2
-1r = 2

Divide each side by '-1'.
r = -2

Simplifying
r = -2
Subproblem 2
Set the factor '(6 + -1r)' equal to zero and attempt to solve:

Simplifying
6 + -1r = 0

Solving
6 + -1r = 0

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

Add '-6' to each side of the equation.
6 + -6 + -1r = 0 + -6

Combine like terms: 6 + -6 = 0
0 + -1r = 0 + -6
-1r = 0 + -6

Combine like terms: 0 + -6 = -6
-1r = -6

Divide each side by '-1'.
r = 6

Simplifying
r = 6
Solution
r = {-2, 6}