Consider the following function. f(x) = x2 − 4x (a) Find the critical numbers of f. (Enter your answers as a comma-separated list.) x = $$2 (b) Find the open intervals on which the function is increasing or decreasing. (Enter your answers using interval notation. If an answer does not exist, enter DNE.) increasing $$(2,[infinity]) decreasing $$(−[infinity],2) (c) Apply the First Derivative Test to identify the relative extremum. (If an answer does not exist, enter DNE.) relative maximum (x, y) = $$DNE relative minimum (x, y) = $$2,−4