In solving the equation (x + 3)(x – 3) = -8, Eric stated that the solution would be
x + 3 = -8 = x = -11
or
(x – 3) = -8 = x = -5
However, at least one of these solutions fails to work when substituted back into the original equation. Why is that? Please help Eric to understand better; solve the problem yourself, and explain your reasoning.

Question

In solving the equation (x + 3)(x – 3) = -8, Eric stated that the solution would be
x + 3 = -8 => x = -11
or
(x – 3) = -8 => x = -5
However, at least one of these solutions fails to work when substituted back into the original equation. Why is that? Please help Eric to understand better; solve the problem yourself, and explain your reasoning.

anonymous · Answer

eric is not playing with a full deck

anonymous · Answer

Do I really have to solve? Because it seems like Eric already solved it... hehe, but one of the solutions are extraneous in that through the process of simplifying the equation you ended up with a solution that was not needed and was only to assist in getting to the real solution.