Expert: Ahmed Salami - 6/10/2004

Question

 Find the domain of the function.  f (x) = 5x / (x2 - 9)  

Answer
Hi Anthony,
To find the domain of any function you look for points where the function is undefined.  This normally includes negatives under radicals and zeros in the denominator of a fraction.  
So for f(x) = 5x/(x^2 - 9)= 5x/(x-3)(x+3)
we have f(x) to be defined everywhere except at x = -3 and 3
Therefore the domain is every point on the number line with the exclusion of x = -3 and 3
You could also write this as
- infinity <= x < -3,  -3 < x < 3 , and 3 < x <= infinity
I hope you are fine with this.
If not, get back to me on it or any othe problem.