a For what values of x is the function f x x2 251 differentiable Enter your answer using interval notation x Find a formula for f x b Sketch the graph of f if x if x f x f x f x 30 10 10 20 10 4 20 10 10 20 10 5 10 10 5 5 10 10 10 10 30k 40 O X 40 DO 40 40 20 X Do 20 20 Sketch the graph of f f x f x f x f x 40 20 40 20 20 20 10 10 X X X Y X 40 20 20 40 20 20 20 10 10 20 10 10 201 20 10 10 20 20 10 DO f x 30 10 10 20 30 10 20 20 20