Index Notation
Maths: Edexcel IGCSE Higher, topic 1.4.2
Powers (Indices)
Powers tell us how many times to use a number in multiplication.
52 means 5 × 5 = 25 and this is a square number
53 means 5 × 5 × 5 = 125 and this is a cube number
5n means n copies of 5 multiplied together
- 5n is called ‘5 raised to the power of n’
Roots
Roots are the opposite of powers.
Square root
- √25 means the number that squares to give 25 and so is +5 or -5 which we write as ±5.
- There will always be a positive and a negative square root.
Cube root
- 3√125 means the number that cubes to give 125 and so is 5.
- Note that (-5)3 = -125 so there is only one cube root.
nth root
- n√x means the number that when raised to the power of n gives x.
- There will be positive and negative roots if n is even, and only a positive root if n is odd.
Test yourself on Index Notation
What is 22?
What is 32?
What is 43?
What is 12?
Which of these is 125?