-3 -2 - N Select all the points at which the graph above is not differentiable 0-4 0-2The graph of f(x) is shown below. Estimate and list the value of x where f(x) has a horizontal tangent. 10 -9 -8 -7 -6 -5 -4 -3 -2 -1/ 1 2 3 4 5 6 7 8 9 10 X =