2.1 Graphs of equations

The Rectangular Coordinate System x-axis origin y-axis

Each point in the coordinate system corresponds to an ordered pair (x,y) Example: (3,5) The first number is called x-coordinate and the second number is called y-coordinate (3,5)

Plotting Points When you plot the points, always look for the numbers on the x-axis (horizontal line) first: negative # is on the left, positive is on the right, then move up (if +) or move down (if -) Ex: Plot (-2,3) And (0, -4) (-2, 3) (0, -4)

More examples (1, 5) (-4, -4) (-1, 3) (6,0) (0, 2) (0,0) (4, -5) (0, -3)

Graphing equations Steps Create a table with x and y Give x at least 3 values if it is a linear equation, if not, give x more values Find y Form ordered pairs Plot the ordered pairs Connect the graph

Example 1 Graph y = 2x + 1 x y = 2x + 1 -1 1

Example 2 y = x2 – 4 x y = x2 – 4 -2 y = (-2)2 – 4 = 4 – 4 = 0 -1 1 2

y = |x| x y = |x|

Ex: y = 1/x x y = 1/x