Question

How can the sum of cubes, x^3 - 27, be written in factored form?

(x+3)(x^2+3x+9)

(x+3)(x^2-3x+9)

(x-3)(x^2+3x+9)

(x-3)(x^2-3x+9)

Answer 1

(x -3)(x² +3x +9)

Explanation:

The sum of cubes is factored as ...

... a³ + b³ = (a +b)(a² -ab +b²)

For a=x, b=-3, this is ...

... x³ -27 = (x -3)(x² +3x +9)