GCSE Maths (Edexcel)

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Negative Indices

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Number Structure and Calculation

Negative Indices

4:54 Indicies & Roots
Spec N7
Previous LCM & Prime Factorisations Next Product Rule for Counting
  • A negative index is an index with a minus sign in front of it.
  • A number to the power of minus 1 is equal to the reciprocal of the number.
  • A number with a negative power is the same as the reciprocal of the number with an equal but positive power.
  • The identity a to the power of minus x is equal to one over a to the power of x holds true for all values of the algebraic variable.
  • To evaluate a number with a negative power, rewrite it as the reciprocal of the number with a positive power.
  • The method of rewriting the right side of the identity a to the power of minus x is equal to one over a to the power of x can be used to solve problems.
  • The identity can be used to convert a fraction with a power in the denominator to index form.

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