Without a graphics card that laptop will have no way to send a video signal to the screen.
It's like having a desktop PC with an Intel Core 2 Duo/Quad, Phenom II X2/X4/X6 or Athlon II X2/X4 CPU and no graphics card or integrated graphics core at all. When you power up the PC and turn the monitor you will get a blank screen because there is nothing connecting the monitor to the PC.
Thank you for your help. It makes sense. The graphic card is very expansive, close to $200. Is there anyway that I can check the laptop is good before buying a graphic card? If I don't use the laptop to run game, is there any cheaper graphic card to use?