When factored completely, the expression p^4 - 81 is equivalent to
(1) (p^2 + 9)(p^2 - 9)
(2) (p^2 - 9)(p^2 - 9)
(3) (p^2 + 9)(p + 3)(p - 3)
(4) (p + 3)(p - 3)(p + 3)(p - 3)

P⁴ - 81
p⁴ + 9p² - 9p² - 81
p²(p²) + p²(9) - 9(p²) - 9(9)
p²(p² + 9) - 9(p² + 9)
(p² - 9)(p² + 9)
(p² + 3p - 3p - 9)(p² + 9)
(p(p) + p(3) - 3(p) - 3(3))(p² + 9)
(p(p + 3) - 3(p + 3))(p² + 9)
(p - 3)(p + 3)(p² + 9)

The answer is (3).

Ab=dc ac=de ad=bce i hope this !