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EL-9900 Graphing Calculator
NotesStep & Key Operation Display
9-4
Use the cursor to check the position
of each point. (Zoom in as necessary).
Points in the solution region
are (2.8, -1.4) and (-8, 4).
Points outside the solution
region are (-1.6, 1.8) and
(-2, -5).
2-2
Substitute points and confirm
whether they are in the solution
region.
.
(-1.6, 1.8): -1.6 + 2 ✕ 1.8 = 2
➞ This does not materialize.
.
(-2, -5): -2 + 2 ✕ (-5) = -12
(-2)
2
+ (-5) = -1
➞ This does not materialize.
.
(2.8, -1.4): 2.8 + 2 ✕ (-1.4) = 0
(2.8)
2
+ (-1.4) = 6.44
➞ This materializes.
.
(-8, 4): -8 + 2 ✕ 4 = 0
(-8)
2
+ 4 = 68
➞ This materializes.
...
(Continuing key operations omitted.)
2-3
Graphical solution methods not only offer instructive visualization of the solution process,
but they can be applied to inequalities that are often very difficult to solve algebraically.
The EL-9900 allows the solution region to be indicated visually using the Shading
feature. Also, the free-moving tracer or Zoom-in feature will allow the details to be
checked visually.
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