Hi. There are actually two versions of the TI-Nspire, the regular "TI-Nspire" and the "TI-Nspire CAS". The regular Nspire is more like a TI-84 in terms of math capabilities. The Nspire CAS is more like a TI-89. If you are only getting a calculator to pass a math class, stick with the 89. If you learn how to use it, it can do about 90% of the problems encountered in a Algebra II class. The Nspire CAS does almost exactly the same things as the TI-89 except it acts more like a computer when it is used. It will not be any more of a help for an Algebra II class. Also, search the internet for programs for your calculator (
Welcome - ticalc.org) that can do some of the things that are not built into the calculator, such as the distance formula. Good Luck!
Don't buy a regular TI-Nspire. This will be a step backwards for you. If you need to get an Nspire, but the TI-Nspire CAS.
EDIT: You can do radicals with an index other than two on the TI-89. Just hit [diamond] then [9] and "root(" will appear in the line. The syntax is root(radicand, index). If you need to see what all of the functions in the catalog can do, look at the back of the guidebook it came with. This explains and gives examples of how to use most of the functions.