Chapter 1 B-15
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Press F4 (TRACE) and use and/or to move
along the graph of the equation in y1.
Press to jump from the graph of y1 to the graph of
y2. Tracing reveals that guesses for the input values
where these two graph intersect are x »
–
10.6, x »3.8.
Return to the home screen with 2nd EXIT (QUIT) .
Access the SOLVER and enter the equation y1 = y2
as shown on the right. Enter the guess for the left-
most intersection point and solve for x.
Enter the guess for the rightmost intersection point
and solve for x.
The two solutions to the equation, reported to four
decimal places, are x =
–
10.5774 and x = 3.7462.
1.2.3 GRAPHICALLY FINDING INTERCEPTS Finding where a function graph crosses
the vertical and horizontal axis can be done graphically as well as by the methods
indicated in 1.2.2 of this Guide. Remember the process by which we find intercepts:
¥ To find the y-intercept of a function y = f(x), set x=0 and solve the resulting equation.
¥ To find the x-intercept of a function y = f(x), set y=0 and solve the resulting equation.
Also remember that an x-intercept of a function y = f(x) has the same value as the root or
solution of the equation f(x) = 0.
Clear all locations in the
y(x)=
list and enter in y1
f(x) = 4x Ð x
2
Ð 2.
Draw a graph with F3 (ZOOM) MORE F4 (ZDECM) . Press
F2 (RANGE or WIND) and reset yMin to
-
6 for a
good view of all intercepts. Press F5 (GRAPH) .
Even though it is very easy to find f(0) =
–
2, you can
have the calculator find the y-intercept while view-
ing the graph by pressing
TI-85 MORE F1 (MATH) MORE F4 (YICPT)
TI-86 MORE F1 (MATH) MORE F2 (YICPT)
Both View the y-intercept f(0) =
–
2.
