The function f is differentiable on the interval [-1,1]. The table shows the values of f' for selected values of x. Sketch the graph of f, approximate the critical numbers, and identify the relative extrema.
x -1 -0.75 -0.50 -0.25
f'(x) -10 -3.2 -0.5 0.8
x 0 0.25 0.50 0.75 1
f'(x) 5.6 3.6 -0.2 -6.7 -20.1