#### To determine

**To state:** The graph of the function *f* is not differentiable at which the numbers.

#### Answer

The function *f* is not differentiable at −1 and 2.

#### Explanation

**Note:** The function *f* is not differentiable at the point *a,* then it must satisfies any of the following conditions.

(i) The function *f* is discontinuous at the point *a.*

(ii) The function *f* has a corner point at the point *a.*

(iii) The function *f* has a vertical tangent at the point *a.*

From the graph of *f*, it is observed that *f* has a corner point at x=2. That is, *f* has no tangent at that point and it is not differentiable at x=2.

The graph of *f* has a removable discontinuity at x=−1. That is, the limit exists as *x* approaches 0 and f(−1) is defined. But limx→−1f(x)≠f(−1).

Therefore, *f* is discontinuous at x=−1.

Thus, it can be concluded that, *f* is not differentiable at the point x=−1.