HP 42S - Manual (Page 24)

15 +
16 END
When we leave the program mode and go to Solver menu again we select FX program and what we
are going to see is
A B C X
Now just enter the values of A, B, C and a start value for X and we are done.:)
Some interesting things to say are: 1-We can't find complex solutions. 2-In this particular case we
are not limited to the case a≠0. 3-About polynomial equations it is much more interesting to write a
more complex equation like ax
5 bx 4 cx 3 dx 2 e=0 . 4-In any equation we are not limited to
find one specific variable, say X, of course we can find any missing variable. 5-We don't need to use
the solver only for “complex” hard to find solution equations. We can use the solver just to
automate some easy calculations.
Example: Consider the ideal gas equation PV=nRT where R is 8.3144472 J/mol . K.
We can write a program like
01 LBL “GAS”
02 MVAR “P”
03 MVAR “V”
04 MVAR “N”
05 MVAR “T”
06 RCL “P”
07 RCL “V”
08 x
09 RCL “N”
10 RCL “T”
11 8.3144472
12 x
13 x
14 -
15 RTN
16 END
So we will have in the solver menu P V N and T. If we want to know how many mols of a gas is
inside a recipient of 1L at a 10.000Pa and 300K all we have to do is
10000 P 0.001 V 300 T
and we give a try for N, for example 1 N and then pressing N again we have 0.0040mols.