<p>^NSpire is really, really confusing. </p>
<p>The 89 is much more powerful, and because of its power, it’s often not allowed by teachers in their classes and by some standardized tests (ACT bans it). Learn to use both the 84 and 89. You can use both at the same time on the Math II and AP Calc tests (and SAT and any other calculator-permitted AP test).</p>