C1-6 Flashcards
What is a set?
A collection of objects where there is a well defined way of determining whether a given object is included or excluded
What is the associative law of addition
placement of brackets in sum is irrelevant
a+(b+c) = (a+b)+c
What is the existence of additive identity
adding zero leaves number unchanged
a+0 = 0+a = a
What is the commutative law for addition
the order numbers are added doesn’t matter
a+b = b+a
What is the associative law of multiplication
the placement of brackets is irrelevant
a.(b.c) = (a.b).c
What is the commutative law of multiplication
the order numbers multiply doesn’t matter
a.b = b.a
What is the trichotomy law
any real number is either positive, negative or zero
What is closure under addition
If a and b are positive then a+b is positive
What is closure under multiplication
If a and b are positive then a.b is positive
What is this symbol and what does it mean?
∩
Intersection symbol
so A ∩ B contain all elements that are in both sets A and B (smaller list)
What is this symbol and what does it mean?
U
Union symbol
so A U B consists of elements that are in set A and set B (bigger list)
What is the existence of multiplicative identity
1 is the multiplicative identity- leaving the number unchanged
a.1 = 1.a = a
What is the existence of additive inverses
A number and its additive inverse sum to zero
a + (-a) = 0
What is the existence of multiplicative inverses
A number and its multiplicative inverse multiply to give 1
a . a^(-1) = 1
What is the distributive law
here the brackets play a crucial role
a. (b+c) = a.b + a.c
What are the natural numbers?
N - counting numbers
1, 2, 3, 4, …
What are integers?
Z- natural numbers, with their negatives and 0
0, 1, -1, 2, -2, …
What are the rational numbers?
a/b : a, b are integers, b does not equal 0
What is a hypothesis/ premise
something assumed or known to be true
What is a conclusion
outcome reached
What is the modulus of a: |a|
a, a greater than or equal to 0
-a, a is less than 0
also square root of the square of a.
What is a conjecture?
possible/ likely to be true
What is a theorem
conjecture proven to be true
What is a lemma
part of a proof of a theorem
what is a corollary
follows easily from a theorem