| What do these
sequences look like when plotted on a graph? |
From Section
2 you know how to use position-to-term rules (in calculator language and
also in algebraic form), and how to enter sequences into the lists.
Section 4 showed you how to work out their first, second
and third differences. These sequences can be plotted as a graph
First,
ensure the list display has 1,2,3,4.. in L1 and 9, 16, 25, 36... in L2, and the
first second and third differences in L3, L4 and L5 respectively. (See
section 4)
Next the calculator has to be set
up to display a scatter graph using the contents of lists L1 and L2 as
coordinates. Follow these instructions and check the screen displays
below.
| Key
presses |
| Go to STAT PLOT (2nd
Y=) |
 |
| Select On and the
first scatter graph icon, then set Xlist to L1 and Ylist
to L2 |
| |
| Select
WINDOW |
| Select Xmin=0,
Xmax=7, Ymin=0 and Ymax=90 |
| |
Now select GRAPH.
The graph shows points on a curve.
The curve is a quadratic curve. In fact its equation is y = (x+2)2.
Change the sequence in L2 and plot the scatter graph of (L1,L2). You will
probably need to adjust the scales in the WINDOW display each time. Use
some of these examples. What shapes do you get?
| Key
presses |
L1
 5
 L2
|
L1
2
1
L2
|
L1
L2
|
| L1 ^ 3
L2
|
| L1 ^ 3
L1
L2
|
L1 ^ 3
L1
L2
|
| |
|
