If -3 is my only critical number how is (b) wrong?

Consider the following function. fix) = (x + 3}\" (a) Find the critical numbers of 1'. (Enter your answers as a comma-separated list.) x = 3 I (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 (00, 3) X decreasing (3. 00) X (c) Apply the First Derivative Test to identify the relative extremum. (If an answer does not exist, enter DNE.) (3,0 relative maximum (x, y) x l relative minimum (x, y) = ( )N 'l- )