# Thread: Domain help..

1. ## Domain help..

What is the domain of each of the following functions?
1.) f(x) = 3x + 9
2.) f(x) = (4x^3 + 4) / (x ( x + 2) (x - 1))
3.) f(x) = x^3 - x^2 + x - 2 EDIT this is minus sorry

ur going to make this undefined ryt?

2. You're probably looking for the "maximal domain", i.e. the largest subset of IR for which f(x) is real (so finite).

You have to 'watch out' for:
- denominators becoming 0 for some x-value(s).
- negative expressions under (square) roots.

3. Help ive tried learning but Visual Calculus - Drill - Domains of Functions
is different from # 1 and # 3 questions

4. Originally Posted by ^_^Engineer_Adam^_^
What is the domain of each of the following functions?
1.) f(x) = 3x + 9
2.) f(x) = (4x^3 + 4) / (x ( x + 2) (x - 1))
3.) f(x) = x^3 - x^2 + x - 2 ...
Hi,

you have to look for those real numbers x for which the function f will give real values.
As TD! has pointed out there are only a few restrictions. You don't deal with square-roots or logarithms. So the only restriction could be that the denominator becomes zero.

1.) D = x Є IR that means: no restrictions
2.) D = x Є IR\{-2, 0, 1} becaus for these numbers the denominator becomes zero
3.) D= x Є IR that means: no restrictions

EB