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7-8 Solving Equations

 The Y–register (press ) contains the previous estimate for the root or equals

to zero. This number should be the same as the value in the X–register. If it is

not, then the root returned was only an approximation, and the values in the

X– and Y–registers bracket the root. These bracketing numbers should be

close together.

 The Z– register (press  again) contains D-value of the equation at the root.

For an exact root, this should be zero. If it is not zero, the root given was only

an approximation; this number should be close to zero.

If a calculation ends with the   , the calculator could not converge on

a root. (You can see the value in the X–register — the final estimate of the root — by

pressing  or  to clear the message.) The values in the X– and Y–registers

bracket the interval that was last searched to find the root. The Z–register contains

the value of the equation at the final estimate of the root.

 If the X– and Y–register values aren't close together, or the Z–register value

isn't close to zero, the estimate from the X–register probably isn't a root.

 If the X– and Y–register values are close together, and the Z–register value is

close to zero, the estimate from the X–register may be an approximation to a

root.

Interrupting a SOLVE Calculation

To halt a calculation, press  or , and the message “” will

be shown. The current best estimate of the root is in the unknown variable; use



 to view it without disturbing the stack, but solving cannot be resumed.

Choosing Initial Guesses for SOLVE

The two initial guesses come from:

 The number currently stored in the unknown variable.

 The number in the X–register (the display).



HP 35s User Manual

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