Here

⇒ ⇒ Graphical solution :

The graph of the function is shown alongside,

From the graph it is clear that the function is continuous at all real x , also differentiable at all real x except at Since sharp edges at and .

At we see that the slope from the right i.e. , R.H.D. = 2, while slope from the left i.e. , L.H.D.= 0

Similarly, at it is clear that R.H.D. = 0 while L.H.D.

= – 2

Trick : In this method, first of all, we differentiate the function and on the derivative equality sign should be removed from doubtful points.

Here, (No equality on –1 and +1)

Now, at while and

at while

Thus, is not differentiable at .

Note : This method is not applicable when function is discontinuous.