How to factor (x+1)^3 - 64

I keep getting (x - 3)(x^2 + 4x + 21)
But it should be (x - 3)(x^2 +6x + 21)

How do I get the right answer?

(x + 1)^3 - 64
(x + 1)^3 - (4)^3
(x + 1 - 4)[(x + 1)^2 + 4(x + 1) + 4^2]
(x - 3)(x^2 + 2x + 1 + 4x + 4 + 16)
(x - 3)(x^2 + 6x + 21) <--This answer is correct

Check your work again, I think you made a mistake somewhere.

(x + 1)^3 - 64

This is a difference of cubes.

((x + 1) - 4)((x + 1)^2 + 4(x + 1) + 16)
(x + 1 - 4)(x^2 + 2x + 1 + 4x + 4 + 16)
(x - 3)(x^2 + 6x + 21).


Hope this helped.

you cant factor that