I have the answer, but can someone show me how to solve it step-by-step? Thank you.

Determine the open intervals on which the function is increasing and on which the function is decreasing. Enter o to indicate the interval is empty. f (x) = 3x3 + 9x2 + 9x + 2 f ' ( x ) = 9 x + 18 x+9 A Increasing on (-0o, -1) ; Decreasing on (-1, co) Q ( x + 2 x + !> B) Increasing on (-0o, oo) ; Never decreasing (D) 9 ( * + 1 ) ( * + R ) C) Increasing on (-1, co) ; Decreasing on (-0o, -1) X = - 1 X = -7 D) Never increasing (0) ; Decreasing on (-0o, co)