Page 28 - 'Blast_Into_Math

Blast into Math! ets of nummers: mathematical plaagrounds

3 Sets of numbers: mathematical

playgrounds

Some people think that math is just about numbers; what do you think? Actually, most mathematicians
spend more time working with mathematical ideas than with numbers. One of the most famous unsolved
math problems, to prove or disprove the Riemann Hypothesis, is about understanding the set of all
prime numbers.

3.1 Set theory

Definition 3.1.1. A set is a collection of elements.

The elements of a set could be numbers, functions, letters, names: anything can be the element of a set.
We use braces {} to surround the elements of a set, for example the set whose elements are the letters
a , b , and c is written

{a, b, c}.

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