hich is equivalent to (9 y squared minus 4 x)(9 y squared + 4 x), and what type of special product is it? 81 y Superscript 4 Baseline minus 16 x squared, a perfect square trinomial 81 y Superscript 4 Baseline minus 16 x squared, the difference of squares 81 y Superscript 4 Baseline minus 72 x y squared minus 16 x squared, a perfect square trinomial 81 y Superscript 4 Baseline minus 72 x y squared minus 16 x squared, the difference of squares