Both (m + n)2 and 36 are perfect squares, and 12(m + n) is twice the product of (m + n) and 6. Since the middle term is positive, the pattern is (a + b)2 = a2 + 2ab + b2. Place the x2 tile, 4 x-tiles and 4 1-tiles in the grid. Fill the outside sections of the grid with x-tiles and 1-tiles that complete the pattern.