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Laws of indices - OCRFractional indices - Higher

An index, or power, is the small floating number that appears after a number or letter. Indices show how many times a number or letter has been multiplied by itself.

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Fractional indices - Higher

Explore updated revision resources for GCSE Maths: Higher - 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 the multiplication rules from earlier 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

\(8\frac{1}{3} = 2\)

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

Simplify \(27\frac{-2}{3}\)

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