When Isolvei Can't Find A Solution; Obtaining More Information About - HP -22S Owner's Manual

When
I
SOLVE
I
Can't Find a Solution
There are two general situations where
'SOLVE
I
may fail to find a
solution:
• 'SOLVE
I
may be unable to find a value that sets the left side of the
equation equal to the right side. The HP-22S displays
NO ROOT FND.
For example, the equation:
ABSOO +Y=0
has no solution when Y
>
0, since IXI can never be negative .
• 'SOLVE
I
may encounter a math error if an estimate generates an
unallowed operation. For example, attempting to solve:
X+Y-12=Z
for X with Y=O displays
D I V I DE BY 0.
See appendix B for additional information.
Obtaining More Information About
I
SOLVE
I
Results
Appendix B covers this topic in more detail.
More Information About Answers. When
'SOLVE
I
returns an an-
swer, pressing .,
LAST
I
displays the value
left - right,
where
left
and
right
are the values of the left and right sides of the equation when
the answer is substituted into the equation. The value in LAST should
be zero or a very small number.
More Information About NO ROOT FND. When ,
SOLVE
I
returns
NO ROOT FND,
press [[] to display the final estimate for the un-
known. Then, press .,
LAST
I
to display the value of
left-right,
where
left
and
right
are the values of the left and right sides of the equation
when the estimate is substituted into the equation.
More Information About Math Errors. When ,
SOLVE
I
returns a
math error, press ,
RCL
I
unknown variable
to view the final estimate.
Sometimes this value can help you diagnose why ,
SOLVE
I
failed to
find a solution.
90 6: Evaluating and Solving Equations