What are the solutions to the equation x (x + 1) = 0?

A. x = 0 only

B. x = 1 only

C. x = 0 or x = 1

D. x = 0 or x = - 1

The answer is D: x = 0 or x = - 1

Proof:

Solve for x over the real numbers:

x (x + 1) = 0

Split into two equations:

x = 0 or x + 1 = 0

Subtract 1 from both sides:

Answer: x = 0 or x = - 1