# Thread: More of a theory question

1. ## More of a theory question

Hey,
i just learned about functions and my teacher said that there is no real inverse function for graphs which are not linear... im guessing this means parabolas and hyperboles... What is the rule defining whether a graph is a function or not?

Any help to clear this would be appreciated

2. Originally Posted by Yesme
Hey,
i just learned about functions and my teacher said that there is no real inverse function for graphs which are not linear... im guessing this means parabolas and hyperboles... What is the rule defining whether a graph is a function or not?

Any help to clear this would be appreciated
This problem was discussed in detail here: http://www.mathhelpforum.com/math-he...ntal+line+test

3. Originally Posted by Yesme
Hey,
i just learned about functions and my teacher said that there is no real inverse function for graphs which are not linear... im guessing this means parabolas and hyperboles... What is the rule defining whether a graph is a function or not?

Any help to clear this would be appreciated
If what you say is an accurate reflection of what your teacher has said (correct, not quoted out of context etc.) then your teacher is wrong.

By a suitable restriction of the domain, non-linear graphs can be defined to be one-to-one and under such circumstances there certainly is an inverse function.

ps: Good memory, earboth!

4. ## thanks alot

thanks.. that really cleared things up =)