functions

[Zfuss12]

I know how to see that a graph is not a function by using the verticle line test, but how do you prove a graph isn't a function mathematically?

 

[stapel]

You could try to solve for a unique "y=". If you fail (like with a circle equation -- the "plus-minus" prevents uniqueness), then the equation isn't a function.

There are more technical methods....

Eliz.

 

[pka]

how do you prove a graph isn't a function mathematically?”
Consider all the ordered pairs in the given graph.
If there could possibly be two different pairs with the same first term then the graph is not that of a function.

For example, the graph of x<SUP>2</SUP>+y<SUP>2</SUP>=4 contains the pairs (0,2) and (0,−2), therefore it is not a function.

 

[jsbeckton]

You have to take it as a case by case basis. There is no quick formula for it, you just get used to things that you know make it not a function like squaring the y term. Picturing the graph is the easiest way(IMO), and as you take more and more math you will have an Idea of what a lot of functios look like right away.

 

[Rylannic]

DOMAIN OF A RATIONAL FUNCTION

I would like to know how to find the domain of a RATIONAL function

 

[stapel]

Re: DOMAIN OF A RATIONAL FUNCTION

I would like to know how to find the domain of a RATIONAL function

Please post new questions as new threads (by clicking on the "new topic" button) rather than as replies to old threads (which is sometimes viewed as "hijacking"). Thank you.

Meanwhile we can't teach classes here, so, for a lesson on rational functions, try here or here.

Eliz.