2.3.1

Identities & Proofs

Test yourself

Proofs

To prove an 'identity', show one side is the same as the other. The identity symbol is . E.g - Show that (n + 3)(n + 2) - 3n + 2 n2 + 2n + 8:

Proofs and Counter Examples

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General numbers in proofs

  • If we are proving something involving an even number, use 2n.
  • If we are proving something involving an odd number, use 2n + 1.
  • Consecutive numbers are shown by n, n + 1, n + 2, ... etc
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Counter examples

  • A counter example is the simplest way to prove a statement is wrong.
  • You only need one counter example to show something is wrong.
  • To disprove the statement ‘The product of two primes is always odd':
    • Use the counter example of the primes 2 and 3 whose product is 6 which is even.

Jump to other topics

1Number

1.1Using Numbers

1.2Fractions, Decimals & Percentages

1.3Powers & Roots

1.4Accuracy

2Algebra

2.1Introduction to Algebra

2.2Manipulating Algebra

2.3Proofs & Functions

2.4Straight Line Graphs

2.5Common Graphs

2.6Transformations & Tangents

2.7Properties of Graphs

2.8Solving Equations

2.9Inequalities

2.10Sequences

3Ratio

4Geometry

4.1Introduction to Geometry

4.2Triangles & Quadrilaterals

4.3Transformations

4.4Circle Basics

4.5Circle Theorems

4.6Measurements & Units

4.7Calculating Area

4.8Triangle Formulae

4.93D Shapes

4.10Vectors

5Probability

6Statistics

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