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EL-9900 Graphing Calculator
Solving a System of Equations by Graphing or Tool Feature
A system of equations is made up of two or more equations. The calculator provides the
Calculate feature and Tool feature to solve a system of equations. The Calculate feature
finds the solution by calculating the intersections of the graphs of equations and is useful
for solving a system when there are two variables, while the Tool feature can solve a linear
system with up to six variables and six equations.
Note that the x and y coordi-
nates are shown at the bot-
tom of the screen. The answer
is : x = - 0.41 y = -0.83
1. Solve the system using the Calculate feature.
2. Solve the system using the Tool feature.
Enter the system of equations
y = x
2
- 1 for Y1 and y = 2x for Y2.
View the graphs.
1-1
Solve a system of equations using the Calculate or Tool feature. First, use the Calcu-
late feature. Enter the equations, draw the graph, and find the intersections. Then,
use the Tool feature to solve a system of equations.
1-2
Find the right-hand intersection by
accessing the Calculate feature again.
1-4
The answer is : x = 2.41
y = 4.83
Example
Find the left-hand intersection using
the Calculate feature.
1-3
7-1
y = x
2
- 1
y = 2x
5x + y = 1
-3x + y = -5
{
{
Y=
—
1
ENTER
2
2
2
2nd F CALC
2nd F CALC
Before
Starting
NotesStep & Key Operation Display
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.
Set viewing window to “-5 < X < 5”, “-10 < Y < 10”.
As the Tool feature is only available on the Advanced keyboard, example 2 does not apply to the
Basic keyboard.
ENTER ENTER
5
(-)
5
X/
/T/n
X/
/T/n
GRAPH
WINDOW
x
2