HP 39gs Master Manual page 140

(iii) Find t so that
N = 2N
The value of is the y intercept of the line of best fit. These values
N
0
from the curve of best fit are not directly accessible but can be retrieved
using the function (see page 135). This is shown in the screen
PREDY
shown right. Store the results into memories
to re-type them from the
Now switch to the Solve aplet and enter the equation to be solved.
Changing into the
NUM
already defined (that was why we stored the curve values into the
appropriate memories), so move the highlight to T and press
Result: Doubling time is 1.0536 hours.
Note: An alternative to this would be to only retrieve the value of
and store it into
same.
.
0
and
A
screen.
view, you should find the values of A and K
. The Solve equation could then be
A
. This saves having
K
.
N
0
PREDY(T)=2*A
140
and the result would be the