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).

(1) is the answer because when you multiply it back you will get p ^ 4 - 81