Can you use an FX lens on a DX camera body?

I have a nikon D3000, which is dx, and i would like to know if i could use an fx lens on it

Yes you can. Actually, almost all of Nikon's top lenses - 50mm f1.4, f2.8 constant aperture zooms - are FX lenses that will perform perfectly on your D3000.

Proshooter's answer might be confusing to you. You absolutely can use an FX lens on your camera. You will see EXACTLY what the image will look like in the viewfinder before you take the picture. His answer makes it sound like you will lose some of what you see in the viewfinder, but you won't.

Technically, he is correct. The FX lens throws a larger image circle, but the sensor only uses part of the potential image.

I use FX lenses on my DX camera almost every day. No problems.

Yes, no problem.

http://www.kenrockwell.com/...ns.htm#top

The lens mount and connections should be the same.
The only major difference is the size of the image on the sensor. The edges of the FX image will be lost but you will get a full size DX image.

I use many full frame (or FX) lenses on APS_C size sensor cameras

http://aviewfinderdarkly.com.au/2007/09/12/how-to-use-old-lenses-on-a-digital-slr/