HP 39g Master Manual page 119

Move the cursor near to the left hand
intersection and then change back to the NUM
view. When you do so, the approximate value
you chose with the cursor is transferred as
your first 'guess'.
Now press and you will see the hp 39g+
find the nearest solution to your guess. Finish
by pressing to verify that the solution is
valid. See page 114 regarding this.
Obviously the next step is to change back to
the PLOT view, move the cursor near to the
second intersection and
If we now change the active variable then there is an immediate change in
the PLOT view to reflect this.
Change back to the NUM view and restore the
variables to the original values, this time
leaving the highlight on C.
Since the active variable is now C, substitution
of all other values means that
becomes ⋅ + = ⋅
0 4 C
are linear and this is shown in the PLOT view.
Notice that the axis label is now C. This would
have only one solution and there would be no
need to supply any particular starting value.
If we duplicate this process for A then
substitution of values means that
+ = ⋅ becomes
2
A B * C 5* B
sides are still linear, although not the same as
before, and this is shown in the PLOT view.
Notice that the axis label is now A.
for that one too.
+
2
A B *
. In this case both sides
0 5
A − = ⋅ . Both
1 0 5
= ⋅
C 5* B
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