0=r(r+3)

Solution for 0=r(r+3) equation:

Simplifying
0 = r(r + 3)

Reorder the terms:
0 = r(3 + r)
0 = (3 * r + r * r)
0 = (3r + r2)

Solving
0 = 3r + r2

Solving for variable 'r'.
Remove the zero:
-3r + -1r2 = 3r + r2 + -3r + -1r2

Reorder the terms:
-3r + -1r2 = 3r + -3r + r2 + -1r2

Combine like terms: 3r + -3r = 0
-3r + -1r2 = 0 + r2 + -1r2
-3r + -1r2 = r2 + -1r2

Combine like terms: r2 + -1r2 = 0
-3r + -1r2 = 0

Factor out the Greatest Common Factor (GCF), '-1r'.
-1r(3 + r) = 0

Ignore the factor -1.
Subproblem 1
Set the factor 'r' equal to zero and attempt to solve:

Simplifying
r = 0

Solving
r = 0

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

Simplifying
r = 0
Subproblem 2
Set the factor '(3 + r)' equal to zero and attempt to solve:

Simplifying
3 + r = 0

Solving
3 + r = 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 + r = 0 + -3

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

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

Simplifying
r = -3
Solution
r = {0, -3}