HP 15c User Manual

Page 182

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182 Section 13: Finding the Roots of an Equation

Keystrokes

Display

´ b 0

001–42,21, 0

Begin with b instruction.
Subroutine assumes stack
loaded with x.

3

002– 3

-

003– 30

Calculate x 3.

*

004– 20

Calculate (x – 3)x.

1

005– 1

0

006– 0

-

007– 30

Calculate (x – 3)x – 10.

| n

008– 43 32

In Run mode, key two initial estimates into the X- and Y-registers.
Try estimates of 0 and 10 to look for a positive root.

Keystrokes

Display

*

| ¥

Run mode.

0

v

0.0000

Initial estimates.

10

10

You can now find the desired root by pressing ´_ 0. When you do
this, the calculator will not display the answer right away. The HP-15C uses
an iterative algorithm

to estimate the root. The algorithm analyzes your

function by sampling it many times, perhaps a dozen times or more. It does
this by repeatedly executing your subroutine. Finding a root will usually
require about 2 to 10 seconds; but sometimes the process will require even
more time.

Press ´_ 0 and sit back while your HP-15C exhibits one of its
powerful capabilities. The display flashes running while _ is
operating.

*

Press ´• 4 to obtain the displays shown here. The display setting does not influence the operation

of _.

An algorithm is a step-by-step procedure for solving a mathematical problem. An iterative algorithm is one

containing a portion that is executed a number of times in the process of solving the problem.

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