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Laws of indices - EdexcelFractional indices - Higher

Indices are used to show numbers that have been multiplied by themselves. They can be used instead of the roots such as the square root. The rules make complex calculations that involve powers easier.

Part of MathsNumber

Fractional indices - Higher

Find out our updated revision resources for GCSE Maths: 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

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

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

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