# How do you rationalize the denominator?

##### 1 Answer

When you have a root (square root for example) in the denominator of a fraction you can "remove" it multiplying and dividing the fraction for the same quantity. The idea is to avoid an irrational number in the denominator.

Consider:

you can remove the square root multiplying and dividing by

This operation does not change the value of your fraction because

Now you can multiply in the numerator and denominator:

Now a problem for you; what happens when the root is not alone???!!!

If you have:

You can use the same technique but...what do you use to multiply and divide?

HINT: look at what happens if you do this: