Main problem

Can you rationalise the denominator of the following fractions?

To rationalise the denominator, we need to multiply by something which gives us an integer as an answer.

How do we do this when there are square roots in the denominator? How could we adapt that method (or those methods) to help us here?

  1. \(\dfrac{1}{1+\sqrt[3]{2}}\)

    (If you need some suggestions on how to get started, have a look at the Suggestion section.)

  2. \(\dfrac{1}{2+\sqrt[3]{2}}\)

  3. \(\dfrac{1}{\sqrt[3]{2} + \sqrt[3]{4}}\)

  4. \(\dfrac{1}{1 - \sqrt[3]{2} + \sqrt[3]{4}}\)

What happens if we change the signs in the final problem? Can you rationalise the denominators in these two fractions?

  1. \(\dfrac{1}{1 + \sqrt[3]{2} + \sqrt[3]{4}}\)

  2. \(\dfrac{1}{1 + \sqrt[3]{2} - \sqrt[3]{4}}\)

You might like to suggest other fractions to rationalise, and apply the techniques you have developed to those. Can you find any fractions for which you cannot rationalise the denominator?