Question: what is the formula of x3-y3?
Answer: Then this is a sum of cubes and we can apply the sum of cubes formula: a 3 + b 3 = (a + b) (a 2 − a b + b 2 ). Substituting a = x and b = 3 into the formula yields: x 3 + 27 = (x + 3) (x 2 − 3 x + 9).