Question 163945
The domain of a rational function will be all the values that you can safely replace a variable with in the denominator of your fraction without producing division by zero, which does not exist.

SAMPLE:

Find the domain of R(x) = (x + 2)/2x

In this sample question, the domain will be ALL REAL NUMBERS EXCEPT THAT X CANNOT = 0.  

Why can't x be zero in the given fraction?

Well, if you replace x with zero in the denominator and multiply it by the number 2 that is already there, you will get 0.

LOOK:

Denominator = 2x

If x = 0, then 2 times 0 = 0

We cannot divide by zero.  This does not exist.  In your math book they call it UNDEFINED.

So, what is the domain in the sample function above?

DOMAIN = ALL REAL NUMBERS EXCEPT THAT X CANNOT BE 0.

Is this clear?