Given the rational function f(x)2x(x-4) for what x-vaule is the function undefined?

Answer 1

It isn't clear exactly what your function is; some symbols disappear when you post a question.In general, rational functions are undefined when their denominator is zero; so you need to solve the equation:

(denominator) = 0

Answer 2

Unfortunately, the browser used for posting questions is hopelessly inadequate for mathematics: it strips away most symbols. We can only see "f(x)2x(x-4)". From that it is not at all clear what the missing symbols (operators) might be. Judging by the question, I am guessing the correct version is f(x) = 2x/(x - 4). If that is the case then the answer is x = 4.