Question

Which of the following is a factor of x3 − 729?

Answer 1

(x - 9)(x² + 9x + 81)

Explanation:

x³ - 729 ← is a difference of cubes and factors in general as

a³ - b³ = (a - b)(a² + ab + b²)

note 729 = 9³ ⇒ a = x and b = 9

x³ - 729 = (x - 9)(x² + 9x + 81) ← in factored form