Consider the following function. fix) =x3 +8 (a) Find the critical numbers of f. (Enter your answers as a comma-separated list.) x=|0 v (b) Find the open intervals on which the function is increasing or decreasing. (Enter your answers using interval notation. If an answer does not exist, enter DNE.) increasing A decreasing | DNE L (c) Apply the First Derivative Test to identify the relative extremum. (If an answer does not exist, enter DNE.) relative maximum (x, y) = ( DNE ) 4 relative minimum (x, y) = ( DNE ) 4