Education Technology

# Knowledge Base

## Solution 30491: Correcting Issues Graphing the Finance Balance Bal() Function on the TI-Nspire™ Family Handhelds and TI-Nspire Family Software.

### Correcting issues graphing finance balance Bal() function on the TI-Nspire Family Handhelds and TI-Nspire Family Software.

When graphing the Bal() function on the TI-Nspire family handhelds you will most likely not see a graph in function graphing mode. This is due to the expression generated by the Balance function being a list of values and the calculator is attempting to create a continuous line. There are two ways graph the Balance function which are listed below:

Using the mortgage example:
Term = 360 Months
Interest Rate = 7.29%
Loan Amount = $550,000 Monthly Payment =$4000

Function Graph in Discrete Mode:

• Open a Graphs page by pressing [Home] and using the cursor to select the [Graphs] icon on the bottom of the screen.

• Enter in a balance function with the parameters listed above by typing the function listed below then press [Enter]:

bal(x,360,7.29,550000,-4000,0,12,12)

• Modify the windows settings to the parameters within the balance function domain by pressing [Menu] [4] [1] and enter the values below:
Xmin=0
Xmax=360
Ymin=-300000
Ymax=550000

• Save the window settings by pressing [Enter]
• Change the graph to discrete mode and step size to 4 by pressing [Tab] and [Up Arrow] to go back to f1(x). Then, press [Ctrl] [Menu] [3] [Down Arrow] [Down Arrow] [Down Arrow] [Right Arrow] [Down Arrow] [4] [Enter] [Enter].

Please Note: Step size cannot be decreased below 4 to show additional points. At step size of 4 the calculator will only generate 89 points of the graph at every 4th value. This is caused by the calculator’s limitation of only being able to display 99 points in discrete graphing mode.

Sequence Graph:

• Open a Graphs page by pressing [Home] and using the cursor to select the [Graphs] icon on the bottom of the screen.

• Switch to sequence graphing mode by pressing [Menu] [3] [6] [1]

• Enter in a balance sequence with the parameters listed in the example by typing the parameters below then pressing [Enter]:
Sequence Expression = bal(n,360,7.29,550000,-4000,0,12,12)
Initial Terms = 0
Sequence Range = 0<n<360
Sequence Step = 1

• Modify the windows settings to the parameters within the balance sequence domain by pressing [Menu] [4] [1] and enter the values below:
Xmin=0
Xmax=360
Ymin=-300000
Ymax=550000

• Press [Enter] twice to save the window settings and graph the sequence.