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Laws of indices - EduqasFractional indices - Higher

Using indices, we can show a number times itself many times or as another way of writing a square or cube root. Indices make complex calculations that involve powers easier.

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Fractional indices - Higher

Find the refreshed revision resources for GCSE Maths: What are fractional indices?, with step-by-step slideshows, quizzes, practice exam questions, and more!

An example of a fractional index is \(g^{\frac{1}{3}}\). The of the fraction is the of the number or letter, and the of the fraction is the power to raise the answer to.

By using multiplication rules it is clear to see that:

\(g^{\frac{1}{2}} \times g^{\frac{1}{2}} = g^1\)

Therefore: \(g^{\frac{1}{2}} = \sqrt{g}\)

In general, \(a^{\frac{1}{2}} = \sqrt{a}\), \(a^{\frac{1}{3}} = \sqrt[3]{a}\) and so on.

Example

\(8^{\frac{1}{3}} = \sqrt[3]{8} = 2\)

It is possible to combine fractional indices with raising a power to a power \(a^{\frac{m}{n}} = (\sqrt[n]{a})^m\).

Question

  1. Write \(t^{\frac{3}{2}}\) in root form.
  2. Simplify \(8^{\frac{2}{3}}\).

It is possible to have negative fractional indices too.

Example

\(27^{\frac{-2}{3}}\).

\(27^{\frac{-2}{3}}=(\sqrt[3]{27}){^{-2}}=3^{-2}=\frac{1}{3^{2}}=\frac{1}{9}\)