Web plots are a really interesting representation of the behavior of a recursive sequence, and you can use the TI-84 Plus to graph web plots. Web plots actually look a little like spider webs. Following are a few ground rules when working with web plots:

**Sequence must be recursive:**The sequence is required to have one level of recursion*u*(*n*–1); using*u*(*n*–2) is not allowed.**Sequence cannot reference***n*directly.**Sequence cannot reference any defined sequence except itself.**

Here, you use the recursive sequence, *a*_{n} = –1/2(*a*_{n–1}), where *a*_{1} = 8.

Here are the steps to enter and graph a web plot in your calculator:

Press [2nd][ZOOM] to access the Format menu.

Use the arrow keys to navigate your cursor to Web in the top row and press [ENTER].

Press [Y=] to access the Y= editor.

Enter the recursive formula for

*u*(*n*).Use

*u*(*n*–1) for the previous term.Enter

*u*(*n*Min).Enter the initial term in the sequence as shown in the first screen.

Press [ZOOM][6].

If you aren't sure what the graph of the web plot will look like, a ZStandard graphing window is a good place to start, as shown in the second screen.

The line graphed at

*y*=*x*is not part of the web plot; it is called the reference line.Press [TRACE] and press the right-arrow key repeatedly to draw the web.

See the third screen. The web plot helps you see that this sequence converges.

To clear a webplot, press [2nd][PRGM][ENTER].