B-14 TI-85/TI-86 Graphing Calculators
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Notice that you could have typed the v(t), with input
variable t, directly in the solver. The solution is, of
course, the same.
If there is more than one solution to an equation, you need to give the solver an approximate
location for each answer. Suppose you are given q(x) = 8x
2
+ 54.65x Ð 163 and asked to find
what input(s) correspond to an output of q(x) = 154. (The procedure outlined below also
applies to finding where two functions are equal.)
Enter 8x
2
+ 54.65x Ð 163 in one location, say y1, and 154
in another location, say y2, in the y(x)= list.
(Remember that if the input variable in the equation
is not x, you must rewrite the equation in terms of x to
graph using the y(x)= list.)
To better obtain a guess as to where y1 equals (intersects)
y2, graph the equations.
If you are not told where you want to view the graph,
begin by pressing GRAPH F3 (ZOOM) F4 (ZSTD) or
GRAPH F3 (ZOOM) MORE F4 (ZDECM ) .
You want to see a ÒgoodÓ graph, that is, one that shows
all the important features. In this case, the important
features are where y1 and y2 intersect.
Neither this graph nor the previous one is a good graph
for viewing the intersections.
To improve the view, use EXIT F2 (RANGE or WIND) * and
change to xMin =
–
15, xMax = 8, yMin =
–
300, and
yMax = 400 . Draw the graph with F3 (GRAPH) .
(There are many other windows that work just as well
as the one shown to the right. Also, instead of setting
a window manually, you could draw the graph with
ZFIT in the ZOOM menu.)
*The current settings for the graphics screen are obtained with GRAPH F2 (RANGE) on the
TI-85 and with GRAPH F2 (WIND) on the TI-86. When the screen appears, the word
RANGE is at the top of the TI-85 screen and the word WINDOW is at the top of the TI-86
screen. Because the only difference in the calculators in this situation is the name that is
used, we from this point forward refer to this key for both calculators as
F2 (RANGE or WIND) . In such cases, the screen shown in the right column will be the one
from the TI-85.
