The Number System Flashcards
What are natural numbers?
All positive numbers without zero
What are whole numbers?
All positive numbers with zero
What are integers?
All negative and positive numbers
What are rational numbers?
All numbers that can be written as a fraction
What are irrational numbers?
All numbers that can’t be written as a fraction
What are real numbers?
All numbers
What does ∈ mean?
Belongs to
What does ∉ mean?
Doesn’t belong to
What is a cardinality and how is the cardinality of set A (ex) written?
It’s the number of elements in a set. Ex: n(A)
What does {} or Ø mean?
Empty set
What does ⊆ mean?
Subset
What is the formula to find the number of subsets of a set?
2^n, where n is the number of elements in the set
What is the universal set?
The set that contains all sets being considered
What is the formula to find the number of proper sets of a set?
2^n - 1, where n is the cardinality of the set
What is a proper set?
When two sets aren’t equal
What is an improper set?
When two sets are equal
What are the properties of real numbers?
1) Commutative: a + b = b + a
2) Associative: a + (b + c) = (a + b) + c
3) Identity: 0 for addition, 1 for multiplication
4) Inverse: +) a -> -a x) a -> a^-1 or 1/a
5) Distributive: a (b + c) = ab + ac
What does ≈ mean?
Approximately
How can you tell if a number is significant or not?
1) Non-zero numbers are always significant
2) In-between zeros are always significant
3) Leading zeros are never significant
4) Trailing zeros are sometimes significant (if there’s a decimal)
