What is the factorization of 49b^ 2 - 81?

(7b - 9) (7b + 9)

Step-by-step explanation:

Each term is a perfect square, so the expression is the difference of squares. In general, that factors as ...

p^2 - q^2 = (p - q) (p + q)

Here, you have p^2 = 49b^2, so p = 7b; and q^2 = 81, so q = 9. Then the factoring is ...

(7b - 9) (7b + 9)