HP 17bII User's Manual | Page 242

HP Calculators User's Manual - 17bII.
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242  B: More About Calculations 

File name : English-M02-1-040308(Print).doc   Print data : 2004/3/9

Iterative Solutions 

If the Solver is not able to isolate the unknown variable, it cannot 
provide a direct solution. In these cases, the Solver searches iteratively 
for a solution.

 
In its iterative search for a solution, the Solver looks for a value that sets 
the left side of the equation equal to the right side. To do this, the Solver 
starts with two initial estimates of the answer, which we’ll call estimate 
#1 and estimate #2. Using estimate #1, the Solver calculates values for 
the left and right side of the equation (

LEFT and RIGHT) and calculates 

LEFT  minus  RIGHT  (LEFTRIGHT). Then, the Solver does the same 
calculations for estimate #2. If neither estimate produces a value of zero 
for 

LEFTRIGHT, the Solver analyzes the results and produces two new 

estimates that it judges to be closer to the answer. By repeating this 
process many times, the Solver narrows in on the answer. During this 
search, the calculator displays the two current estimates and the sign of 
(

LEFTRIGHT) for each estimate, as shown. 

 

 

Sign of LEFT

-RIGHT for each estimate 

 
 

Since calculators cannot do calculations with infinite precision (the hp 
17bII+  uses  12  digits  in  its  calculations), sometimes the Solver will be 
unable to find an estimate where 

LEFTRIGHT is exactly zero. However, 

the Solver can distinguish between situations where the current estimate

 

could be a solution, and situations where no solution is found. 
 

 

* Exceptions: (1) Occurrences of the unknown variable as the argument of the S 

function are ignored. (2) The unknown variable can appear twice within an IF 
function: once in the then clause and once in the else clause. 

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