An easy question that I can't seem to do.

Show that (2√2+2)² = 12+8√2

The method I have been taught is the grid method (diagram below is meant to be a grid I can't seem to draw it so use your imagination :P ):

......2√2.......2

2√2..X.......4√2

.

2.....4√2......4

But I can't do 2√2 x 2√2. Some help? I can work its meant to be 8 so I can do the question but how would I do that?