i just bought a book of arpeggios from my local music store and it has pretty much every arpeggio ever. now it is mainly a reference book but it was only 13 dollars and the theory book was 19, so i bought this one. now my problem is that there are 4 positions for each arpeggio that go all across the fretboard. do i need to learn every position or can i just learn the one with the root note starting first. i know how to play the pentatonic scale all across the fretboard but i usually only use one or two positions. any advice would be helpful.

thanks, and sorry bout the long post.
You can learn only one shape but it's better to learn most of them, since it will be easier to switch from one arpeggio to another. So basically the more you know the easier it will be for you to play.
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No problem. It's up to you really. If you plan on doing sweeps and stuff like melo-death/shred guitar solos it could be useful but if your doing indie music I'd stick with the first 2 positions.