HP 39gs Master Manual page 160

As can be seen in the screen shots right, the bottom half of the screen
shows the roots (if any), the value of the discriminant and the equation in
the form y=ax 2 +bx+c.
The key labeled
screen. Possible values for the increment are 0.5, 1 and 2.
Pressing on the calculator, or the screen key labeled
SYMB
change the emphasis from the graph to the equation in the right hand
half of the screen. Pressing
will change the emphasis from the equation back to the graph.
SYMB mode
The alternative to graphical mode is symbolic mode. In
directly and see the changes reflected in the graph.
For example, on the screen shown below, the 'v' coefficient is high­
lighted and can be changed using the
changes to 'h' and 'v' is controlled by the
range of values is available for the values of 'a' as in
You can move from one coefficient to the next by using the
keys.
As with the mode, the equation in y=ax
and its discriminant are shown on the right half of the screen.
The + and - keys are disabled in
controlled instead by the
coefficient. The key controls the sign of 'a'.
Test mode
The final key is labeled
series of graphs for which they must supply the equation. The type of graph is governed by the current setting
of . For example, if the current setting of
only use the v parameter instead of a, h and v simultaneously. The setting of
the screen using the key supplied.
changes the 'step size' of the movements on the
on the calculator, or the key labeled
PLOT
and
2
mode, since their effects are
and keys once the highlight is on the 'a'
. This key will present the student with a
will
mode the student can change the coefficients
keys. The size of the
key, and the same
mode.
and
+bx+c form, its roots
was at Y
= +
2
X
160
v then the test graphs would also
can be changed within