<p>All of my teachers recommended the TI-83 or 84 simply because it’s what they use in class. You could get away with the 89 (though you might want to consider getting the 83 if you want to take the ACT.) </p>
<p>Don’t get the TI-84. It’s more expensive than the TI-83, yet not that much better. If you can get a good deal on the 84 and it’s cheaper, then go ahead though.</p>