HP 42S manual

15+

16END

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 ax5bx4cx3dx2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”

118.3144472

12x

13x

14-

15RTN

16END

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.