# Tips & Tricks - Sequences & Series; Defining A Generalized Gp And The Sum To N Terms; Solving Sequence Problems - HP 39g Master Manual

Graphing calculator.

T
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T
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R
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K
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Q
U
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N
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E
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### Defining a generalized GP and the sum to n terms.

If we define our
GP using memory
variables then it
becomes far more
flexible.
The advantage of this method is that you now
need only change the values of A and R in the
HOME view to change the sequence.
Defining a series
(sum to n terms of
a sequence) is
fairly straight-
forward using a
similar method.
Note the reference to U1 in the definition of U2.
Once U2 is defined in this way you can change both U1 & U2. by simply
storing new values into A and R.

### Solving sequence problems

Questions like "What term is the first to be greater than 10 000?" or
"When does S
first exceed 10 000?" can be answered in the NUM view.
n
Simply move into the N column, make an
inspired guess as to the term you require and
type it in. The table jumps to that value.
For example, in answer to the first question,
we estimate N=35. However we find that
U1(35) is far too large. By successive
guesses, we find that T
is the one we were
15
seeking. The second problem is as easily
solved in this way.
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