Answer:
(3x-4) (3x+4)
Step-by-step explanation:
9x^2-16
9x^2 is a product of squares = (3x)^2
16 is a product of squares = 4^2
so
9x^2-16 is the difference of squares
(a^2 - b^2) = (a-b) (a+b) where a = 3x and b =4
9x^2-16 = (3x-4) (3x+4)