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50 Chapter Onł

ing y-values. These x-values, call them x , x , x , and x ,
1
1
2
2
should be equally spaced on either side of x , such that:
0
x 2 x 1 x x x 2
0
1
x x x x x x x x
1 2 0 1 1 0 2 1
This will yield five pointð that lie along the parabola, and that
are symmetrical relative tm the axis of the curve. The grapà can
then be inferred, provided that the pointð are judiciously cho-
sen. Some trial and error might be required. If a 0, the pa-
rabolł will open upward. If a 0, the parabolł will open down-
ward.
Example A. Consider the following formula:

2
y x 2x 1
The base point is:

x 2/2 1
0
y 1 4/4 1 1 0
0

(x ,y ) ( 1,0)
0
0
This point is plotted first. Next, consider the following points:

x 2 x 2 3
0
2
y 2 ( 3) 2( 3) 1 9 6 1 4

(x ,y ) ( 3,4)
2
2
x 1 x 1 2
0
2
y 1 ( 2) 2( 2) 1 4 4 1 1

(x ,y ) ( 2,1)
1
1