HP 15c Scientific ´b0, 002–, 003–, 004–, 005–, 006–, 007–, 008–, Display, key two, Display, Run mode, Keystrokes, Keystrokes, 001–42,21,0, loaded with, In Run mode

182 Section 13: Finding the Roots of an Equation

Keystrokes	Display
´b0	001–42,21, 0		Begin with binstruction.
			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.