Relations & Functions Flashcards
set
a well-defined collection of objects, which are called the elements of the set
empty set
∅ = {} = {x | x ≠ x}
set of natural numbers
N = {1, 2, 3, …}
set of whole numbers
W = {0, 1, 2, …}
set of integers
Z = {…, -3, -2, -1, 0, 1, 2, 3, …}
set of rational numbers
Q = {a/b | a ∈ Z and b ∈ Z}
set of real numbers
R = {x | x possesses a decimal representation}
set of irrational numbers
P = {x | x is a non-rational real number—that is, a decimal that does not repeat or terminate}
set of complex numbers
C = {a + bi | a,b ∈ R and i = √-1}
interval
the set of all real numbers lying between two fixed endpoints with no gaps
intersection of two sets
A ∩ B = {x | x ∈ A and x ∈ B}
union of two sets
A ∪ B = {x | x ∈ A or x ∈ B (or both}
Quadrant I
x > 0, y > 0
Quadrant II
x < 0, y > 0
Quadrant III
x < 0, y < 0
Quadrant IV
x > 0, y < 0
(a, b) and (c, d) are symmetric about the x-axis if
a = c and b = -d
(a, b) and (c, d) are symmetric about the y-axis if
a = -c and b = d
(a, b) and (c, d) are symmetric about the origin if
a = -c and b = -d
to reflect (x, y) about the x-axis,
replace y with -y
to reflect (x, y) about the y-axis,
replace x with -x
to reflect (x, y) about the origin,
replace x with -x and y with -y
the distance between points P(a, b) and Q(c, d) is
d = √[(c – a)² + (d – b)²]
the midpoint M of the line segment connecting P(a, b) and Q(c, d) is
M = [(a + c)/2, (b + d)/2]
relation
a set of points in the plane
the graph of x = a is
a vertical line through (a, 0)
the graph of y = b is
a horizontal line through (0, b)
the fundamental graphing principle
The graph of an equation is the set of points which satisfy the equation. That is, a point (x, y) is on the graph if and only if x and y satisfy the equation.
x-intercept
a point on a graph which is also on the x-axis
y-intercept
a point on the graph which is also on the y-axis