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3.1 Graphing The Rectangular Coordinate System Quadrant I Quadrant II x-axis origin Quadrant III Quadrant IV 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) (3/2,3) (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 at least 5 values – Find y – Form ordered pairs – Plot the ordered pairs – Connect the graph Example 1 • Graph y = 2x + 1 x -2 y = 2x + 1 » Y = 2(-2) + 1 = -4 + 1 = -3 0 Y = 2 »(0) + 1 = 0 + 1 = 1 (0, 1 ) 2 Y = 2(2) +1 = 4+1=5 » (2, 5 ) (-2, -3) Continue… Y=2x +1 Order pairs (-2,-3) (0,1) (2,5) • Y = (1/2)x + 2 For equation with fractions, what numbers should we choose for x?