36-9r=r*r

Solution for 36-9r=r*r equation:

Simplifying
36 + -9r = r * r

Multiply r * r
36 + -9r = r2

Solving
36 + -9r = r2

Solving for variable 'r'.

Combine like terms: r2 + -1r2 = 0
36 + -9r + -1r2 = 0

Factor a trinomial.
(3 + -1r)(12 + r) = 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 '(12 + r)' equal to zero and attempt to solve:

Simplifying
12 + r = 0

Solving
12 + r = 0

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

Add '-12' to each side of the equation.
12 + -12 + r = 0 + -12

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

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

Simplifying
r = -12
Solution
r = {3, -12}