Get the latest information and updates on GPRC’s response to COVID-19
Skip to Main Content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.



Some of the content of this guide was modeled after a guide originally created by the Openstax and has been adapted for the GPRC Learning Commons in September 2020. This work is licensed under a Creative Commons BY 4.0 International License.

Adding and Subtracting Rational Expressions


CASE 1) Adding and Subtracting Rational Expressions with Common Variable Denominators: in this case, we only need to add/subtract the numerators.
Example: Subtract
We only need to subtract the numerators:


CASE 2) Adding and Subtracting Rational Expressions with Unlike Variable Denominators: in this case, we find a common denominator first and then proceed with the addition or subtraction.


Example: Add
To add these rational expressions, we need to find their common denominator. Since the denominators have nothing in common their common denominator is equal to their product:.
So, we multiply the first fraction by and multiply the second fraction by:

We then expand the numerators of each expression and add them together:


Grande Prairie Campus
10726 - 106 Avenue
Grande Prairie, AB T8V 4C4
Phone: 1-780-539-2939
Fairview Campus
11235-98 Avenue
Fairview,AB T0H 1L0
Phone: 1-780-835-6750