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EL-9900 Graphing Calculator
10-2
There may be differences in the results of calculations and graph plotting depending on the setting.
Return all settings to the default value and delete all data.
Solving Absolute Value Equations
The absolute value of a real number x is defined by the following:
|x| = x if x
≥
0
-x if x
≤
0
If n is a positive number, there are two solutions to the equation |f (x)| = n because there
are exactly two numbers with the absolute value equal to n: n and -n. The existence of two
distinct solutions is clear when the equation is solved graphically.
Example
Solve an absolute value equation |5 - 4x| = 6
1
Enter y = |5 - 4x| for Y1.
Enter y = 6 for Y2.
2
View the graph.
There are two points of in-
tersection of the absolute
value graph and the hori-
zontal line y = 6.
3
Find the points of intersection of
the two graphs and solve.
The solution to the equation
|5 - 4x|= 6 consists of the two
values -0.25 and 2.75. Note
that although it is not as intu-
itively obvious, the solution
could also be obtained by
finding the x-intercepts of the
function y = |5x - 4| - 6.
The EL-9900 shows absolute values with | |, just as written on paper, by
using the Equation editor. The graphing feature of the calculator shows the
solution of the absolute value function visually.
GRAPH
Y=
MATH
B
15
4
6
2
2
2nd F
CALC
2nd F
CALC
ENTER
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Before
Starting
NotesStep & Key Operation Display
X/
/T/n