I have a single 1000W bulb in my flowering room that is 8 X 8 feet. Light coverage is OK. You can use them in separate rooms - one for vegging and one for flowering. If you want both in one room measure the far wall and divide by 3. If the room is 9 feet place one bulb 3 feet from the left wall and the other 3 feet from the right wall. You may want to leave a little room on each side wall for access. I took a large sheet of paper with tape on it and moved it around the ceiling for my flowering room. Gave me a good visual idea of where to hang the light fixture.
Good luck, BigSteve.