I have a CASIO fx-991ES PLUS and its amazing.
Can integrate/differentiate (not factorise, give you answers), you can do graphs (it gives you values when x=1, 2, 3 etc.) and a lot of stuff.
You can also do the simpson's rule and pythaorian rule too (instead of working it one by one, with different 'h', it gives it to you with the difference you want)
