Answer:
81(x + 2y)(x - 2y)
Step-by-step explanation:
[tex]81 {x}^{2} - 324 {y}^{2} \\ \\ = {(9x)}^{2} - {(18y)}^{2} \\ \\ = (9x + 18y)(9x - 18y) \\ \\ = 9(x + 2y) \times 9(x - 2y) \\ \\ = 81(x + 2y)(x - 2y)[/tex]
