Shinna wants to factor $9x^{2}y^{4} – z^{6}$. “Wait!” she says. “I think I can see a way to use the difference of squares factoring pattern!”

1. Is Shinna’s expression a difference of squares? If so, what are the “squares”? If not, explain why.

   Answer (a):

   Yes; it is the difference of the square $\left(3xy^{2}\right)^{2}$ and the square $\left(z^{3}\right)^{2}$.

2. Help Shinna factor the expression $9x^{2}y^{4} – z^{6}$.

   Hint (b):

   Remember that one factor contains addition and the other subtraction.