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Introduction to Rational Functions - Problem 1 4,098 views

Teacher/Instructor Alissa Fong
Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

Find the domain of f(x) equals 4/x. Okay so domain remember is the set of all possible input or x numbers that would keep my function defined. A function would be undefined if it had 0 in the denominator. That makes this problem pretty easy.

When it says find the domain I know that x can be any number, any real number except for what, do you know? It is except for 0, except 0. Because if x were equal to 0 this function would be undefined. If you were to graph it you’d find that‘s an asymptote or what we call an excluded value. The domain is x could be any real value except for 0 and the reason why is because thou shall not divide by zero. It’s an undefined function if you have 0 on the denominator.