Help with Duel monitor setup please

I have an early 09 iMac running latest OS and with it just bought the new 5k iMac. I would like it be able to use my older iMac as a second display for school work. I am taking intro to 3D and other classes and having a duel monitor set up would make life a lot easier. Unfortitly everything I have read doesn't really say how this is done of if it can be down at all. From what I have read and if I am understanding it at all, I need a mini display cable to mini display cable and that will get me the duel screen i'm looking for. Is this true? any ideas on how to make this happen? Thanks mac community. Also if you have any questions about the 5k iMac feel free to ask. It's completely maxed out in every way and I am loving it so far.

file:///Users/Luke/Documents/specs.tiff

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