Yes. The two calculators are the same more or less overall. They have the same functions and features. There are slight differences (eg: the TI84 is slightly faster than the 83 version), but it's not too big a deal since you can do the same math with both versions.
If you can, I recommend using online tools such as Desmos or GeoGebra. These tools are much faster compared to the TI83 and TI84. Also, they allow for multiple colors to be used, so you can tell the graphs apart. There are lots of other features as well (way too many to go over right now), and the best part is that both tools Desmos and GeoGebra are free. Unfortunately, your teacher may not allow you to use them in a test setting. However, I would ask and they may allow a limited version to be used in some capacity.
