A polynomial is factored using algebra tiles.

An algebra tile configuration. 0 tiles are in the Factor 1 spot and 0 tiles are in the Factor 2 spot. 15 tiles are in the Product spot in 3 columns with 5 rows: 1 is labeled + x squared, 2 are labeled + x, the 4 tiles below + x squared are labeled negative x, and the 8 tiles below the + x tiles are labeled negative.

Which polynomial was factored?