When we leave the program mode and go to the 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. For polynomial equations it is more generally useful to write a more complex equation like
ax
4
+ bx
3
+ cx
2
+ dx + e = 0. We can set the coefficients of the higher order terms to zero if
we want to solve a lower order polynomial.
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.
6. We ordinarily do not need to enter a starting guess for the variable we are solving for — just
press that menu button without keying a value first, and the Solver will solve for it.
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 ×
09 RCL “N”
10 RCL “T”
11 8.3144472
12 ×
13 ×
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 moles of an ideal gas
is inside a container of 1L at a 1000Pa pressure and at 300K all we have to do is10000 P 0.001 V
300 T and we give a try for N, for example 1 N and then pressing N again we have 0.0040
moles.
8 Numeric Integration
Suppose we want to solve numerically a integral of the form
∫
b
a
dxxf )(
We write the function in the same way we did in the solver case.
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