### Concept (1)

We have rational expressions whenever we have a fraction that has a polynomial in the numerator and/or in the denominator. An excluded value in the function is any value of the variable that would make the denominator equal to zero. To find the domain, list all the values of the variable that, when substituted, would result in a zero in the denominator.

### Sample Problems (4)

Need help with "Definition and Domain of a Rational Expression" problems? Watch expert teachers solve similar problems to develop your skills.

Domain for:

x − 3
x + 2
###### Problem 1
How to find the domain of a rational expression.

Simplify:

x − 1
x² − 4x + 3
Domain:
###### Problem 2
How to simplify and find the domain of a rational expression.

Simplify:

5 − x
x − 5
Domain:
###### Problem 3
How to cancel opposites in a rational expression.

Simplify:

x² − 5x + 6
4 − x²
Domain:
###### Problem 4
How to simplify a rational expression that contains opposite factors.
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