Checking solutions – HP 48g Graphing Calculator User Manual
Page 356
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25
Interpreting Results from the Multiple Equation Solver
The Multiple-Equation Solver solves for variables by repeatedly
looking through the set of equations for one that contains only one
variable that’s “unknown” (not user-defined and not found by the
solver during this solution)—then it uses the HP 48 root-finder to find
that value. It continues eliminating “unknown” variables until it solves
for the variable you specified—or until it can’t solve for any more
variables. Each time the Multiple-Equation Solver starts solving for a
variable, only the variables with black menu labels are “known.”
During the solution process, the Multiple-Equation Solver shows the
variable it’s currently solving for. It also shows the type of root found
by the HP 48 root-finder (zero, sign reversal, or extremum)—or the
problem if no root is found (bad guesses or constant). (You can
watch the iterations if you press any key except
(CANCEL
) during the
root-finding process. For more information about the root-finder, see
chapter 18.
The following messages indicate errors in the problem setup:
■ Bad Guess variable. For a list of guesses, at least one of the list elements must have consistent units, ■ Too |■ ‘1.эny Unknowns. The solver eventually encountered only equations having at least two unknowns. Either enter other known ■ Constant? The initial value of a variable may be leading the root finder in the wrong direction. Supply a guess in the opposite Checking Solutions The variables having a a: mark in their menu labels are related for the If any solutions seem improper, check for the following problems: 25-10 The Equation Library
values, or change the set of equations—whichever is appropriate for
your problem. See “Changing the Equations” later in this chapter.
direction from a critical value—if negative values are valid, try one.
most-recent solution—they form a compatible set of values satisfying
the equations used. The values of any variables without marks may
not satisfy the equations because those variables weren’t involved in
the solution process.