Just to clear up any confusion, hecticar, x≠−1. Any time a division-by-zero error arises, the entire expression is immediately deemed as undefined--no matter where.
x=−1;−(x−4)(x−1)(x+6)÷(x−7)(x−4)(x+1)(x+6) | Let's just do a quick substitution. |
5−10÷400 | |
We have reached a problem. Do not go any further! Here is another way to think about, I guess.
Any result in the format x0 is given the name "undefined" because it literally does not have a meaning; it is pure nonsense; it means nothing at all. By taking the reciprocal, you are attempting to attach meaning to nonsense, which you should never do.