An algebra tile configuration. only the product spot is shown. 8 tiles are in the product spot in 3 columns with 3 rows. first row: 1 + x squared, 2 + x. second row: 1 +x, 2 +. third row: 1 +x, 1 +. how many more unit tiles need to be added to the expression x2+4x+3 in order to form a perfect square trinomial? 1 2 3 4