Is Mid-2009 MBP Memory compatible with Late-2009 iMac?

Hello,

I just upgraded the memory for my MacBook Pro (from 2 X 2gB to 2 X 4gB).....I was going to sell the used memory but then realized I might be able to add it to my late-2009 iMac. How do I find out whether this is compatible? Currently the iMac only has 4gB in 2 slots but is upgradeable to 16gB and has 4 slots available.

Looking forward to a response and thanks in advance.

J