HP (Hewlett-Packard) HP 33s Calculator User Manual


 
7–8 Solving Equations
File name 33s-English-Manual-040130-Publication(Edition 2).doc Page : 388
Printed Date : 2004/1/30 Size : 13.7 x 21.2 cm
If an equation does not allow certain values for the unknown, guesses can
prevent these values from occurring. For example,
y = t + log x
results in an error if
x
0 (message

).
In the following example, the equation has more than one root, but guesses help
find the desired root.
Example: Using Guesses to Find a Root.
Using a rectangular piece of sheet metal 40 cm by 80 cm, form an open–top box
having a volume of 7500 cm
3
. You need to find the height of the box (that is, the
amount to be folded up along each of the four sides) that gives the specified
volume. A
taller box is preferred to a shorter one.
40
80
40
_
2 H
H
H
80
_
2 HH H
If H is the height, then the length of the box is (80 – 2H) and the width is (40 – 2H).
The volume
V is:
V = ( 80 – 2H )
×
(40 – 2H )
×
H
which you can simplify and enter as
V= ( 40 – H )
×
( 20 – H )
×
4
×
H