HP 48G Series Quick Start Manual page 61

To decide which case it is, you should find the value of the expression
at the Sign Reversal point.
Example: Find the value of the expression at the computed value of
z in order to decide whether it is a solution to RATFUNC
or represents the location of a discontinuity.
Step 1: Press (A) to move the highlight to the Efi: field and press
EuFR=. The value of the expression at the computed value
of z 1s returned to the stack.
Step 2: Return to the stack to view the value of the expression
(labeled Expt).
: 1.5
wi -3. ABRAREEARHT
Eup: 133339933903
I I
Because the value of the expression is not close to zero, in all
likelihood, there is a discontinuity at # = —3. (You can confirm
this by substituting -3 into the original equation and observing
that it generates denominators equal to zero—a sign of a potential
discontinuity.)
In general, whenever you expect multiple solutions, you'll probably
save yourself some time and effort by plotting the expression and using
the graphical analysis tools instead of the SOLVE application (see
lesson 26 for an example).
Press ((2)(SOLVE) ik to return to the SOLVE application and try
solving another equation—this time keying it in yourself.
Example: Find the measure (in degrees) of the largest angle in a
triangle with sides of 4, 7, and 9, with 6 as the largest
angle and c as the largest side). Use the Law of Cosines:
c? =a" + b% — 2abcosb
Solving Equations 5-5