Plot the following points on your graph: (2,0), (0,1), (3,2), (1,3). These give you the four corners of the square. The area of the square is 5 because everything is based on a right-angled triangle with sides 2 and 1. The square on the hypotenuse is equal to the sum of the squares on the other two sides (Pythagoras), so 2*2+1*1=5. The square is tilted to the right.