Algebra Period 4

GRAPHING ORDERED PAIRS:
7-1

Review of x y Coordinate Plane Graphing from Pre-Algebra

Cartesian plane: Named after French mathematician Descartes.


plane: a two dimensional (across and up/down) flat surface that extends infinitely in all directions.


quadrant: 2 perpendicular lines called axes split the plane into 4 regions....

quad means 4
quadrant

names: begin in the top right (where you normally write your name!) and go counterclockwise in a big "C" (remember it for "C"oordinate)


They are named I, II, III, IV in Roman Numerals



coordinate - A coordinate is the position of a point in the Cartesian plane


coordinate = "co" means goes along with (COefficient, COworker, CO-president, CO-champions)



"ordinate" means in order

So coordinate means numbers that go along with each other in a certain order


The numbers are the x and y values and the order is that the x always comes first



Also called an ordered pair (x y "ordered" and they are a "pair" of numbers)


Ordered pairs are recognized by the use of ( x , y ) format



origin = (0, 0) the center of the graph (its beginning or origin)


When you count the coordinate' s position, you count from the origin.



x comes before y in the alphabet so the order is (x, y) 
always go right or left first, then up or down



the x axis is the horizontal axis (goes across)


Remember that because the number line also is horizontal and you learn that first


(the pattern to remember is x is always first and the number line is before going up and down)



NOW LET'S GET TO WHAT YOU ACTUALLY DO!!!


1) Count your x value:


positive x, count right from origin (positive numbers are to the right of zero on number line)


negative x, count left from origin


2) Count your y value:


positive y value, count up from where your x value was (up is the positive direction)


negative y value, count down from where your x value was (down is the negative direction)



EXAMPLE:
(3, 5) Count 3 to the right from the origin, then 5 up


(3, -5) Still count 2 to the right, but now count 5 down


(-3, 5) Count 3 to the left from the origin, then count 5 up


(-3, -5) Again count 3 to the left, but now count 5 down



BUT WHAT HAPPENS WHEN
 ONE OF THE VALUES IS ZERO?


If the y value is zero it means that you move right or left, but don't go up or down:


SO YOUR POINT WILL BE ON THE x AXIS........

x axis is where y = 0 
Example: (3, 0) is a point on the x axis, 3 places to the RIGHT


Example: (-3, 0) is a point on the x axis, 3 places to the LEFT



If the x value is zero it means that you don't move right or left, you just go up or down.


SO YOUR POINT WILL BE ON THE y AXIS...........

y axis is where x = 0 


Example: (0, 3) is a point on the y axis, 3 places UP


Example: (0, -3) is a point on the y axis, 3 places DOWN